Retroarch reads Roms from SD2, but Bios from SD1. I’ve ensured I have the correct folder directory (it’s the same on both SD1 and SD2). No directory options inside retroarch. It’s minor because things work, but I’d like it to be correct and read from SD2 like it does the Roms.
if you have done the migrate to SD2, it should be automatically read from SD2 for both roms and bioses.
Once you move BIOS to sd2 in configuration>storage options, you should have a /muos/bios folder there.
Your bios should be in that folder, since that is the default location for them with muOS.