Managed to find a v2.1 WAD, installed it under 236, and it worked! Thanks for pointing out that 2.2 doesn't work, SNES.
Although it only works with my Sandisk flash drive - it would seem my Seagate 1TB Backup Plus STCA1000100 isn't compatible (I just bought it yesterday for the purpose of putting all my games on, too). Or at least it's not compatible yet, hopefully it will be in a future release. :) [Yes it's FAT32, 32kb-cluster (confirmed by chkdsk), single-partition, primary, and active ;)]