Comment 5 for bug 1848326

Managed to reproduce it:

1) switched to nvidia;
2) worked for a while with it for a while with 5.3.0-19-generic;
3) got a kernel update to 5.3.0-23-generic;
4) switched to intel;
5) reproduced the problem.

What I found is:

1) /lib/modprobe.d/blacklist-nvidia.conf gets created if you switch to "intel";

2) blacklist-nvidia.conf wasn't in initramfs for the new kernel:

lsinitramfs initrd.img-5.3.0-19-generic | grep blacklist-nvidia.conf ; echo $?
usr/lib/modprobe.d/blacklist-nvidia.conf
0

lsinitramfs initrd.img-5.3.0-23-generic | grep blacklist-nvidia.conf ; echo $?
1

3) running `updateinitramfs -u` fixes it.

From what I can see:

* updateinitramfs works correctly and the blacklist file gets created correctly as well so long as "intel" is selected;

* If a kernel is upgraded while the profile is set to "nvidia" though, /lib/modprobe.d/blacklist-nvidia.conf is (correctly) not there so any initramfs generation or updates do not include it;

* So when `prime-select intel` is done on a system that got upgraded with `prime-select query -> nvidia`, there is nothing to update initramfs.