swtpm VS CloverBootloader

Or you can just add a virtual tpm device in virt-manager while setting up the vm using swtpm. It seems to ha e packages on most major distro's.

If you want Windows 11 instead for whatever reason, swtpm can emulate a TPM chip for QEMU to use.

You can find the source of software TPM implementations which abide to the official spec such as: https://github.com/stefanberger/swtpm but that has no real bearings on the TPM used on real hardware

I install swtpm and in virt-manager add a TPM 2.0 emulated device and set the secure boot image before I install. This seems to work well enough.

I don't know either, but apparently Microsoft didn't guarantee that 'unsupported' systems would continue to receive system updates. I just use a QEMU VM and swtpm.

swtpm - a software Trusted Platform Module emulator and the ways of using it;

Seems there are two such projects for that:

https://github.com/stefanberger/swtpm

This should work: https://github.com/stefanberger/swtpm/wiki

Linux has several TPM emulators. This one is probably the most popular. But here's another for TPM 1.2 only. The main use-case is to emulate TPMs for use with Virtual Machine guests.

Other GitHub posts from previous versions seem to have the issue described here but maybe I missed something, https://github.com/stefanberger/swtpm/issues/572 I'm on an arch install and just installed it from pacman.

Definitely look into clover

You need to try and learn it ....clover is a bit eazy then OC https://github.com/CloverHackyColor/CloverBootloader/wiki/Configuration

I did manage to get Clover to boot, turns out it was a graphics card issue (Clover does not boot on ProLiant DL 560 Gen 8) so I threw an old HD 3470 I had laying around in it and I can now access Clover. I gonna play with Clover a little and see if I can get it to do what I want and if not, I grab the Slim ODD to SATA adapter you mentioned. Just need to find the cables to connect it.

In your case you may wish to research using a tool such as Clover Bootloader, which would allow you to install Proxmox to NVMe drives and then put Clover on an internal or external USB thumb drive. The boot process would start from Clover on USB before linking your NVMe installation and continuing from there.

Clover bootloader https://github.com/CloverHackyColor/CloverBootloader

You can use Clover to emulate UEFI on legacy BIOS computers.

Are there any other bootloaders I should be considering? My understanding was that LILO and BURG have essentially been abandoned so even if I were willing to rely on an abandoned project for something as important as the bootloader (I'm not btw) then it probably would not work with LUKS/Btrfs. While doing my initial research, I did come across Clover but I know even less about that than I do about Systemdboot and Refined. My initial impressions is that it seems very customizable theming-wise but it feels like maybe not too many people use it / I'd have a hard time finding help and that's IF it even supports LUKS/Btrfs.

You Clover outdated af (2017). Update to 5123.1, which is the last one with the old memory fixes: https://github.com/CloverHackyColor/CloverBootloader/releases/tag/5123.1