Machine won't boot following clean install of 20.04

[asb3]

I performed a clean install of ubuntu 20.04. The install was successful, and I immediately tried to reboot.
The machine won't boot. After displaying 2 flash screens, it hangs with a black screen except for a cursor in the upper left corner. The cursor is not sensitive to mouse or keyboard.

If I go into BIOS and select as boot device the drive with the new installation, I immediately get the black screen with the cursor.

Before the install, I cloned the drive containing the boot partition to a usb stick. I can boot from the USB stick, and everything is as it was before. If I examine the drive with the new /boot partition, everything is looks OK.

What should I do?

[dino99]

Might be relative to the gpu driver: which one should be used ? If its a nvidia for example, you need the kernel headers & build-essential installed first.
If you can read 'journalctl -b' then you might find some issues about the video

[asb3]

The computer does boot using the ubuntu 20.04 liveCD.

[CelticWarrior]

Disable Secure Boot in UEFI then try to boot normally.

[dragonfly41]

Boot flags set in target?

[asb3]

Original installation had lvm turned off. I reinstalled with lvm turned on, and it worked.

[TheFu]

Please read the Release Notes for 20.04. Many common problems with workarounds are there:
https://wiki.ubuntu.com/FocalFossa/ReleaseNotes

New releases always seem to have some rough spots that take a few months to nail down.