after BIOS update with secure boot lots of issues on Ubuntu 21.10

[kalpana]

Today there was the new BIOS EFCN54WW for my Lenovo Legion 5 15IMH05H 81Y600AJMB laptop.
I have installed dual-boot Ubuntu 21.10 and Windows 11 with secure boot enabled.
After the BIOS update, I had to manually enable secure boot again, select discrete graphics and select Ubuntu as boot partition.
Windows 11 still booted fine.
But Ubuntu 21.10 had no nVIDIA drivers, no screen brightness control, no VMWare modules and failing VirtualBox driver.
Were the secure boot keys in Ubuntu not valid anymore?
As a quick fix I disabled secure boot in the BIOS and Ubuntu was again fully OK.
And guess what: even Windows 11 booted fine, while the requirements list secure boot must be enabled for this OS.

What can I do in Ubuntu to be able to re-enable secure boot?