so you dont have the 3000 series, so its possible the ibt bug…
are you still chrooted?
if so open new terminal window and from this window open this file:
kate /mnt/etc/default/grub
and change this line to look like this:
GRUB_TIMEOUT_STYLE=menu
then in this line: GRUB_CMDLINE_LINUX_DEFAULT inside the quotes add this parameter:
ibt=off
dont remove any parameters from there, add it to existing one, save the file;
and now go back to the chrooted terminal window and here run this command:
update-grub
exit chroot:
exit
reboot and see if it helped
also now you will have a grub menu shown during boot, so you can select the 5.15 kernel in the advanced options - dont select the fallback one, select the normal one