anaconda VS CloverBootloader

I'm on Fedora right now and will probably be keeping that. But aiming to add several linux distros in a multi-boot setup (no Microsoft products involved). The other likely candidates include Nobara, Rocky, OpenSUSE, Alphine, Arch, and Void (haven't decided on which ones or how many yet). I would like to set this up as one big LUKS2 partition with a Btrfs filesystem and each OS organized into its own respective Btrfs subvolume. I'm currently using BIOS mode but planning to reinstall under UEFI. My assumption is that I will need to have multiple boot partitions for however many OSes I plan to go with (haven't done much on UEFI before so I am unclear if distros can "share" a boot partition - particularly Fedora/Nobara/Rocky bc Anaconda has a bug where it removes the boot partition for other Fedora installs).

Anaconda is the installer for Red Hat (and RHEL, and Fedora, and CentOS, and Rocky, and...) and has been forever, much longer than Conda has existed. It is the installer RH distros

It creates a luks volume and places LVM on it, and only adds a 15G root logical volume in LVM.

Anaconda is the name of Fedora's installer.

The issue is that Red Hat broke ISO support in this commit and of course, as a Red Hat derivative, CentOS 8 has the same issue.

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