I'm facing the same problem with Ubuntu 20.04.1 LTS and GeForce 310M, using an old Samsung QX310.
Without these drivers, the preinstalled intel driver works fine.
But with "prime-select intel" I boot into a black screen.
To go back into the DE, first I have to press Ctrl+Alt+F4 and then input my login and password. Sometimes it takes a few tries. I hope this helps others, so that booting into recovery mode is not needed.
I'm facing the same problem with Ubuntu 20.04.1 LTS and GeForce 310M, using an old Samsung QX310.
Without these drivers, the preinstalled intel driver works fine.
But with "prime-select intel" I boot into a black screen.
To go back into the DE, first I have to press Ctrl+Alt+F4 and then input my login and password. Sometimes it takes a few tries. I hope this helps others, so that booting into recovery mode is not needed.