LG calibration studio never supported widegamut monitors until last years and limited to GB-LED backlights, and when I say support I mean proper spectral corrections for their displays. Hence unless you had an old lg31mu97 from ~2016 their calibration never really worked as expected with your i1DisplayPro.
If you has an sRGB only LG display with HW calibration, LG software should support it without issue (It has the proper spectral corrections for that LED family)

Regarding current Dell software for built in sensors it "should" be paired at factory to colorimeter (old basic matrix correction, not like spectral corrections for i1displaypro), but if you have doubts just check:

-get DisplayCAL & ArgyllCMS. No need to install any driver. Just unzip ezecutables and on 1st run of DisplayCAL put the path to uncompressed ArgyllCMS bin folder.
-UP2720Q uses a LED technology that provides almost full AdobeRGB green and P3 red coverage, so this LED is likely to be WLED PFS phosphor, adobergb flavor (which needs an spectral correction close to "HP Z24X G2" bundled with DisplayCAL) or some QLED (which may be found on user made colorimeter corrections like Asus "pa32ucg" ).
-Measure white, or run a full measurement report verifying current display profile (do not use simulation profiles).

This test using one (first one, then the other) of the two suggested colorimeter corrections will shed light on your questions: if Dell software for built in colorimeter is working as expeced.
DisplayCAL measurement report will show a lot on information, take 1st look on "assumed vs measured whitepoint" and "profile vs measure whitepoint" on additional statistics. 1st one will show if white has color tint in green or pink ("whiteness test", the most important), and assumed CCT in kelvin will tell you closest to daylight white (cool-warm, less important) on 100K increments

Validate LG monitor too using, but if you have a widegamut LG monitor first find backlight technology or put model name here so other people can provide you a hit on wghich spectral correction needs to be selected in DisplayCAL so measurements will be accurate.

Many thanks for your comprehensive reply, it's very much appreciated. However, having installed DisplayCAL and ArgyllCMS as instructed I am having trouble getting DisplayCAL (latest version) to run stably on my M1 Macbook Pro. The software constantly hangs / stops responding and will not get as far as allowing me to do a measurement. Until a version comes out that will run properly for me I don't think that will be an option.

Just for my own clarity, if I profile for AdobeRGB using the Dell's built in colormeter and select that within the monitor's menu Color settings, should I also create a profile using my i1DisplayPro on top of that and select that profile in my System Prefs / Display settings, or should the Dell measured AdobeRGB profile alone be providing accurate display colour? That's the bit that's confusing me. Thanks for your help.

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@Dabow wrote:

Many thanks for your comprehensive reply, it's very much appreciated. However, having installed DisplayCAL and ArgyllCMS as instructed I am having trouble getting DisplayCAL (latest version) to run stably on my M1 Macbook Pro. The software constantly hangs / stops responding and will not get as far as allowing me to do a measurement. Until a version comes out that will run properly for me I don't think that will be an option.

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Just for my own clarity, if I profile for AdobeRGB using the Dell's built in colormeter and select that within the monitor's menu Color settings, should I also create a profile using my i1DisplayPro on top of that and select that profile in my System Prefs / Display settings, or should the Dell measured AdobeRGB profile alone be providing accurate display colour? That's the bit that's confusing me. Thanks for your help.

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You can run whitepopint test from commandline.
Go to bin folder and run

dispcal -r -X path_to_your_led_tech.ccss

And it will report whitepoint reading (xyY) and distance to  blackbodu (NO) or daylight curve (YES)  (pink-green) and associated CCT (blue-yellow). => look for "CDT" correlated daylight temp, Kelvin value is assumed WP and dE is somehow a measure of green pink tint.

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Usually nobody (who knows what he ie doing) do this. If you want to use display for photo use, use full native gamut and create an ICC that describes after calibration native status. There is (usually) no point limiting display native gamut to AdobeRGB because you work on AdobeRGB images. Photoshop or any other color managed tool know what to do as long as there is an ICC that describes CURRENT display behavior (display behaving in some OSD preset, whatever it is)

But let's say that for some reason you want your display to simulate AdobeRGB ("liiting display response to AdobeRGB", native gamut is BIGGER, there is no point doing that).
HW calibration software should:
-measure uncalibrated response
-compute a calibration for white, grey and optionally to limit native gamut (simulating an smaller colorspace like sRGB or AdobeRGB)
-upload calibration to display
-Measure after calibration response and create an ICC profile with this measured response.

You software SHOULD do this last step and if it is not doing it, it is bad calibration software. If it is doing that, it should assign that newly created ICC profile to display in OS settings (Windows or macOS, it does not matter), hence in the good scenario you should do nothing.
If it is working properly but is missing last step, sevaral options:
-you can use DisplayCAL in "no calibration just profiling" mode and create an ICC without caring about calibrating grey on GPU. But you said I is not working on your m1.
-use a display profile one ICC profile that matches your "target", this means "I blindly believe that calibration is OK and display is behaving as I requested". In your sample this means using generic AdobeRGB profile as display profile. For native gamut calibrations you can use driver /EDID profile. Also you can always use DisplayCAL's standalone icc synth editor to create a display profile with whatever white, gamma and RGB primaries.

Thanks again for this info, it's very helpful. Okay, good, so if I'm understanding you right all I should need to do is calibrate my UP2720Q using the inbuilt hw colormeter and ensure that the Dell Colour Profile is selected in my Display Settings (see screen cap)- so no need to additionally calibrate again with my i1DisplayPro. Okay, that seems to be fine and I can select the Dell profile. Now it's just a case of checking to see if that calibration is accurate. The reason I'm seeing a colour discrepancy within the orange/yellows on my prints could be an accuracy issue with the paper manufacturers ICC profile I suppose. There's a definite warmer tone when I profile this monitor with my i1DisplayPro though, which is what's been confusing me, but I'm wondering if that's because I had the calibration set to 'Native'. 

Okay, that seems to be fine and I can select the Dell profile.

First of all check if Dell calibration software generated a profile and assigned it to display. It should have asked you for profile name describing your last HW calibration.

If Dell calibration software is not doing this, then you should assign the profile by yourself. Only in that scenario
Default display profile should be selected only If you chose native gamut in calibration and the same target gamma as informed by that profile.
Otherwise you should select as as display profile a custom one from DisplayCAL ("profile only" mode) or if DisplayCAL is not working you should select a profile that is equal to calibration target (AdobeRGB for AdobeRGB calibration target, or a syntheic profile created from arbitrary calibration target with DisplayCAL synth profile editor).

If you use Dell software to calibrate to AdobeRGB target but use "default display profile" (native gamut, autogenerated by macOS when you plugged it) Photoshop will believe that your display red is near P3 red, hence will desaturate red colors sent to image when showing AdobeRGB images. Images will look bad in those red, more orange thna true AdobeRGB red. Same if you calibrate to sRGB but you select default display profile (native gamut), it will desaturate red and green in a bad way.
Display profile on OS settings should always track current display behavior, otherwise color management won't work.

IDNK what Dell calibration osftware means for "Native" or the additional settings you used.
"Native" with no params aims for native gamut, native white, nominal gamma and usually you do not want that (native whitepoint color).
"Native" with whitepoint param and gamma/tone response curve param is a very useful preset.
If Dell software only allows "native" with no params, do not use it. It should have a "Custom xy" mode, use it with your desired white, gamma and native xy coordinates for R, G & B. Your can get native gamut coordinates using displcal -R -X path_to_CCSS.ccss

It seems that you can choose "Native" gamut and custom white:
https://photographylife.com/wp-content/uploads/2020/02/Dell-Calibration-Assistant-960x625.png

Hence if you chose "native" gamut and "D65" white... validate whitepoint as I said to you previously:

You can run whitepopint test from commandline.
Go to bin folder and run

dispcal -r -X path_to_your_led_tech.ccss

It will tell you actual whitepoint after calibration

First of all check if Dell calibration software generated a profile and assigned it to display. It should have asked you for profile name describing your last HW calibration.

It's never asked me for a profile name, but it does seem to have created one as per my last screenshot. And just to be clear, with the UP2720Q I'm referring to the monitor's in-built colormeter and software that are accessed via the monitor buttons. I'm not using any desktop s/w to do this calibration, just the monitor h/w and in-built s/w. If I switch between the UP2720Q created profile and AdobeRGB in Sys Prefs I see no visible difference, so I guess that means that the Dell profile is correct.

If you use Dell software to calibrate to AdobeRGB target but use "default display profile" (native gamut, autogenerated by macOS when you plugged it) Photoshop will believe that your display red is near P3 red, hence will desaturate red colors sent to image when showing AdobeRGB images. Images will look bad in those red, more orange thna true AdobeRGB red. Same if you calibrate to sRGB but you select default display profile (native gamut), it will desaturate red and green in a bad way.

This is good info, thanks.

IDNK what Dell calibration osftware means for "Native" or the additional settings you used.
"Native" with no params aims for native gamut, native white, nominal gamma and usually you do not want that (native whitepoint color).

The UP2720Q has a 'Native' profile which can be selected but cannot be calibrated. I'd assumed this was just the full gamut of the monitor with unrestricted colourspace. When using the i1DisplayPro it was set to 'Native', which is what I meant, so I think that's perhaps where my confusion was coming from. Now that I know I don't need to separately calibrate the monitor again with the i1DisplayPro this is no longer an issue..

So where I'm at now is I've calibrated to AdobeRGB with the Dell monitor inbuilt h/w and s/w and selected that profile in my Sys Prefs. The only thing that isn't happening is it's not asking me to name the profile after calibration, it just seems to be overwriting the existing one in Sys Prefs.

So where I'm at now is I've calibrated to AdobeRGB with the Dell monitor inbuilt h/w and s/w and selected that profile in my Sys Prefs. The only thing that isn't happening is it's not asking me to name the profile after calibration, it just seems to be overwriting the existing one in Sys Prefs.

Maybe it is not doing that. Just read display profile xy RED coordinates, check if those coordinates are AdobeRGB red or near P3 red. Easy to check values in wikipedia. Apple's ColorSync app should allow you to inspect profile's red coordinates (it should be stored on rXYZ tag, ColorSync will print it in CIE XYZ or CIE xy)

If it is doing that so default display profile matches calibration target...all OK. You need to do nothing.

If it is not updating default display profile you'll have to set manually the proper one on OS settings by yourself, and that profile should match display behavior on that OSD mode. My previous messages were about this 2nd scenario.

Also... instead using monitor's physical buttons, use Dell Calibration Assistant software as the screenshot I showed to you from Photography Life review of that model. This will ensure that proper profile is used as OS default display profile.

Brilliant! I didn't even know this s/w existed. Thanks!