With some currently still a bit of hands-on approach you can set up measured boot that can measure everything from the BIOS (settings) through the kernel, the initrd, and also kernel command line parameters.

I currently do not have time for a clear how to, but some relevant references would be:

https://www.freedesktop.org/software/systemd/man/latest/syst...

https://www.krose.org/~krose/measured_boot

Integrating this better into Proxmox projects is definitively something I'd like to see sooner or later.