Comment 0 for bug 1936759

shim-signed package installs with no error with apt upgrade, but then the system cannot boot afterwards with secure boot enabled. System hangs indefinitely on UEFI manufacturer logo screen (Dell in this case), not getting as far as grub. Disabling secure boot is a workaround.

Rolling back to previous shim-signed version 1.46+15.4-0ubuntu1 fixes the problem (system can once again boot with secure boot enabled).

Done this for now to allow secure boot to be enabled:
$ sudo apt install shim-signed=1.46+15.4-0ubuntu1
$ sudo apt-mark hold shim-signed

Details of system where problem is observed:
- Dell XPS 13 7390 laptop
- Intel® Core™ i7-10510U CPU / 16GB RAM
- BIOS/UEFI firmware version: v1.8.0 (latest)
- Ubuntu hirsute 21.04 64bit (Linux only, single OS, not dual booting)
- Kernel version: 5.11.0-22-generic
- GRUB: 2.04-1ubuntu45

Any questions / additional info, please ask.