Finally tried to hook up an AM4 chipset to a raspberry pi (someone suggested this on the pi-pci repository a few years ago), and it turns out it mostly just works.
@coreforge I have a B450 board I'm about to scrap for some unrelated error, is it worth keeping around?
@max If you have a reason to actually do this, it might be. This should work fine for pretty much any chipset from B350 onwards, just firmware loading might be a bit different.