This might be a silly question, but how do I select a kernel to boot
from on the Raspberry Pi?
Use the arrow keys when the menu comes up? I'm not sure from the
details you provide at which point/how you're trying to change this.
I've just installed Fedora 31 on both a Pi2 and a Pi3 and in both
cases
updating the kernel from 5.3.7-301 to 5.4.12-200 results in a broken
display with lots of diagonal interlaced lines. The original kernel is
still present but although the usual grub configuration files are
there, the Pi is obviously ignoring them. Is there a way to boot from
the original kernel?
You make no mention of the image your using. Is it an aarch64 image or
armhfp/ARMv7?