Witches no longer spawning in witch farm

I went to my witch farm today (which was made using a witch hut), and noticed witches are no longer spawning in it, it's only spawning normal mobs (skeletons, spiders, creepers, zombies)
Was working fine before updating to 20w21a.
And now it seems the launcher no longer keeps the previous snapshots listed to be able to play them, the farm is unusable 😞