I would suggest you connect video cable to onboard integrated VGA and boot into Windows.  Go in device manager under Display adapter.  Is there any video card listed other than Intel graphics (which is the integrated gpu)?

If RTX is detected it would show up as some device even without nvidia driver. Also look for any unknown device in dev mgr after you install RTX 

Another important thing to do in legacy 9020 is always replace CMOs battery w a new battery and clear CMOs settings by motherboard jumper. A senile CMOs may fail to detect new gpu.

@redxps630​ thanks for the response. I have connected to the intel graphics via a DisplayPort and I don’t see the gpu in device manager. None of the hidden devices are the gpu and nothing comes from checking for hardware changes. I replaced the cmos battery but don’t know what exactly you’re referring to about the cmos settings or motherboard jumper. I’m assuming a hardwipe wouldn’t really touch the CMOs settings? 

There is a jumper pin called RTCRST or CLR CMOS on motherboard 

move a blue jumper from password to RTCRST for 10 sec then move back 

User validated 

https://www.userbenchmark.com/UserRun/67905606

Try update bios to latest version if not already done.

With the same setup, if the 9020 system is detected and working with the RX 570 (with 6-pin power) and not detected nor working with the RTX 2060 super (with 8-pin power), the issue could be with the RTX card.

@redxps630​ tried it. Have been unable to boot so far after. Trying to get it back to booting. 

After CMOs is cleared, It is normal for pc to take a bit longer time than before to go through POST.  It may restart a few times too with blank screen.  Power button LED should be white. I am confident you will see Dell logo on video via onboard VGA or DP soon if not already 

@redxps630​ perhaps I needed to wait? Either way, it can now boot again and I’ve reset the clock. 

I did remove RAM and GPU in attempts to get it to boot (one of the errors that came up I have faced before and resolved (whether sensible or not) by seating and unseating ram).

back in and still don’t see the gpu. 

I’ve made plans with a friend to hopefully plug the gpu into his machine and see if it’s just a faulty gpu…or I guess a faulty motherboard?

@Bear4life69​ I'd check the BIOS to see if the card is even detected there first. Should be under General -> System Info -> PCI Info. I have a feeling its not as we're not getting anything in device manager. It would also be a good step to reseat the original GPU to ensure its not an issue with the slot. The MT should also have 2 x16 slots, so have you already tried the 2nd slot? It is wired as x4, but it may help to confirm if its detected or not.