Maybe changing SATA operation mode to AHCI could help.

Load Windows with only 1 of the drives installed.  I take it you plan using 1 drive for boot and 1 for storage?

My experience is if there's 2 boot drives with Win10 installed, 1 drive will sabotage the other and give BSOD.

As for Ubuntu showing up, you may need an aftermarket/online drive eraser.  We likely have others in this forum that can recommend some.

Meanwhile, I'm going to suggest reformatting the drive that gives you Ubuntu.  That also wipes everything.  So, if the drive is formatted to NTFS as it should be, you can still go thru the procedure of reformatting it NTFS, and that will wipe it.  I've had to do it myself.  That doesn't exclude still possibly using another program to wipe the drive.

One thing that will cause strange behaviors is if the size 2032 CMOS battery is low.

I'm not 100% certain on getting an mSATA drive to work in a 9020, but I see the micro can take one (userbenchmark) and hopefully the tips help.

have you already tried chino’s suggestion of AHCI.  If bios>sata operation is raid which may be Dell factory default that could prevent normal presence of both mSATA and sata drives in Windows.

Update:

After trying several different tricks, I finally found a solution to the “Ubuntu” problem. I reset the BIOS, and that got rid of the Ubuntu option in the boot menu. But I haven't been able to find a solution to the recognition of the M-SATA drive by Windows 11. I tried erasing both drives using “Darik’s Boot and Nuke” utility (DBAN), before reinstalling Windows, but that didn’t solve the problem either. The only other option I haven’t tried yet is doing a low level format of the M-SATA drive; but it is difficult to do that because it is not visible in Windows—unless I can find an external utility (like DBAN), which doesn’t need to be “installed” on Windows to be used. I should add that I have more than one of these machines. I found them for a good price on eBay. I have another one in which I have installed Windows 11 as well as an M-SATA drive, and it works perfectly well. Windows recognizes it without a problem. But for some reason on this particular machine it doesn’t.

@Chino de Oro's and @redxps630's suggestion (AHCI) + test or replace size 2032 CMOS battery.

There's another step to reset, but I don't think it's necessary since you reset BIOS.  I'll leave it here for if you still want to try it.  Could be you did it already:  How to Perform a BIOS or CMOS Reset and Clear the NVRAM on Dell Computers 

Also, there was a little confusion of where Ubuntu was showing up.  You said on the machine so I thought that meant from a boot drive.  I didn't know it was showing up in BIOS.

Could you please upload a photo of what shows in BIOS (not the boot menu) for boot options?

I tried AHCI, but then it gave me a warning that if I chose this option, my OS might not reboot, or may need to be reinstalled, so I didn’t proceed with it. I also looked at the other computer I mentioned that I have, that works OK, and that was not set to AHCI either, so that does not appear to be the cause of the problem.

The “Ubuntu” option was not showing in the BIOS. It was showing in the boot menu that appears when you press F12 as you boot up the system. I don’t know where it was coming from. All I know is that it only disappeared after I had reset the BIOS

I wonder whether your pc showing only one drive in Windows (either mSATA or SATA) is the result of Intel Smart Response Tech.  9020 is one of the Dell models that use such tech.  Try this if you may, let’s assume your mSATA is 128 GB and your SATA is 500 GB, when you see only one drive in Windows, say only mSATA, does the C: drive size actually say the size is 500 GB?  That would be one sign that Windows is caching mSATA ssd + original SATA to be one logical drive C:.  This is normal and intended.  Refer to this discussion for more read if you like.

If you like to have two drive letters in Windows one for ssd one for hdd, you need to first change to AHCI, then wipe both drives and do a clean install of OS on one drive,  or try this boot trick without having to reinstall OS.

1. Click the Start Button and type cmd
2. Right-click the result and select Run as administrator
3. Type this command and press ENTER:

   bcdedit /set {current} safeboot minimal

4. Restart the computer and enter BIOS Setup
5. Change the SATA Operation mode to AHCI from RAID
6. Save changes and exit Setup and Windows will automatically boot to Safe Mode.
7. Right-click the Windows Start Menu once more. Choose Command Prompt (Admin).
8. Type this command and press ENTER: 

   bcdedit /deletevalue {current} safeboot

9. Reboot once more and Windows will automatically start with AHCI drivers enabled.

Okay, I think the only way you guys are going to believe what I am saying is if I give you a visual demonstration! I just installed Speccy on the computer and ran it, and it identified both drives. But when I go to "This PC" in Windows on the computer, it only recognizes one drive, the "C" drive on which the OS is installed, but not the other drive. I have attacked a screenshot of both windows being open, Speccy as well as "This PC," so you can see it for yourself. The drive is visible in Speccy, but not in Windows:

I offered the solution which should work but you did not try and you keep trying to prove that you are facing the issue.  We do believe you.  If you were to wipe all your drives and perform a clean install of Windows, what keeping you from changing SATA mode to AHCI???

Both of Brad and Red were suggesting the same direction but they offered more details and all the reasonings.  If you read Red post right above your last post, it has value information for you to understand better.

For short, your machine was setup in RAID mode and use a small solid state to cache the hard drive which would improve the performance.  Your goal is to use single, separate drive.  You must break the cache (see Red post to learn how) if you want to retain and keep the current data or you must change to AHCI before reinstall Windows, so proper storage controller can be installed and will show all individual drives.

@harfad 

As for the drive showing in Speccy, but not Windows, this thread is getting long so I'm not 100% sure of it's current status, but:  A drive has to be formatted and drive letter assigned to show in Windows.*  Formatted to NTFS and GPT partition scheme if loading Win10 or 11 on it.  I also use the same for storage HDD's.  *Unformatted drives can still show in BIOS and not Windows.

If a drive was part of a RAID array, that could be a different story until wiped and reformatted.

Win10&11 automatically formats and partitions drive when loading.  It also gives the the option to delete previous partitions when loading.

I also asked for a photo/screengrab of boot options showing in BIOS.  Not that you absolutely have to do it, but that would've so assisted us better.

My 7010 came with boot options related to booting from a network.  They were unbeknownst to me until I was having boot problems after a reload.  Had to uncheck or delete them.

What we're looking for is the drive you want to boot from showing in BIOS, or boot from Windows Boot Manager.  Also was looking for any other nonsense that can cause boot problems.

You said you have other 9010's not having the same problems and BIOS is not on AHCI.  You didn't mention what the other BIOS are set on.