Ugh I had to get an obscure PCIe card working a few years back and it was a huge pain. I believe I ended up having to find the broadcom chipset by model because the generic brand driver didn’t support it, then the arch repos didn’t have the driver for the model, and there were several aur packs available that I had to try one by one. And it was kernel module loaded, so each was a reboot.
Absolute hell of a time, probably about 5 years ago.
I’ve had this happen. I never did figure it out, personally. I distro hopped a bit and eventually ended up back on Arch and it didn’t happen again, so I guess it was a bugged install?