macOS 11.5 fixed the diver load issue (for me)
Ok, uninstalled that extension using their uninstall script... too much fun eh? how are we now?
At least now, everything is within a year or so old. (Installed no later than 2020)
Does SoftRAID auto load with 11.5 now?
Maybe try a "reinstall SoftRAID driver" if not, and see if that helps.