I have installed 20.04 on a Dell OptiPlex 7050, with an Intel HD Graphics 630 (rev 04).
The boot process hangs on the splash screen. This does not happen on the first reboot immediately after installation, but on the next boot after that.
I have some partial solutions by adjusting the line GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub:
Use 'nomodeset' in addition to the default 'quiet splash'. The system boots with the splash screen, but this option seems to disable some graphics functionality permanently (not just during the boot): after booting with 'nomodeset', all compositor animations in gnome-shell are disabled.
Replace 'quiet splash' with 'nosplash'. This works better: the system is both able to boot, and composting animations work. The only downside is that you don't have a splash screen.
Question: It should be possible to have both a splash screen during boot, and working gnome-shell animations. How can this be achieved?
(Personally, I don't really care about the splash screen, but this problem cost me enough time and headache that I wanted to post something for others.)