I found the problem. The culprit is the packet grub2-theme-mint. Last version 1.2.2 When I remove this packet grub initrd works fine with the new kernels. Sorry for the misplaced bug report.
** Changed in: linux (Ubuntu) Status: Confirmed => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1975690 Title: kernel 5.13.0-41 and 5.13.0-44 do not boot To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1975690/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs