Update, I just tested Spectralizer 1.3.4 + OBS 26.1.2 + MacOS 11.2 (Big Sur) on my M1 Macbook Air and it works flawlessly! Thank you @universallp for your work on this!
Oooh. How did you get it to work on your M1 Mac? I just tried but it failed – It doesn't show up as an available source to add in. (It works fine on my old Intel Mac, though).
Any hints much appreciated!