What I really want is to put Mint 20 on my dell-precision-3530, which came preinstalled with Ubuntu.
I installed Mint 19.3 Cinnamon on it without a problem a while back, but not anymore.
The problem is when I try to install Mint 20 on it - the laptop locks up early in the install. The mouse moves, but nothing else happens.
If I boot the installer in compatibility mode, it doesn't crash as quickly, but I can see a kernel oops flash by sometimes. In this case, it crashes the installer is shutting down, and a subsequent forced reboot gives a grub> prompt, not mint.
I contacted Dell about it, but they referred me to Canonical sales. Canonical sales sent me back to Dell, saying this was Dell's responsibility. Dell told me that I should pay for a copy of Ubuntu from Canonical to get help.
I pressed Dell a little about it, and they said that I could get help from Dell if I reinstall the laptop with Ubuntu 18.04, since that was what was on the laptop when it was sold. However, installing Ubuntu 18.04 gives "No boot device found. Press any key to reboot the machine", even if I restore the BIOS to factory defaults.
Also, on this system memtest86+ 5.01 hangs not long after starting to test. I heard that 5.01 has a bug that makes it hang if you use it in SMP mode, so I tried both with and without SMP - it got stuck in the same place each time. I left memtest86+ running overnight not-in-SMP-mode, and it never got any farther. I can see the red "+" in memtest86+ blinking, but other than that there is no sign of progress from memtest86+.
Could someone please suggest a way of either getting Mint 20 to install, or to get Ubuntu 18.04 to boot? I suspect there's a hardware problem, so maybe Ubuntu 18.04 would be better. The laptop is still under warranty.