Meet the new forge, same as the old forge. Forge has been forked, with the majority of forge's developers moving over to the fork, NeoForge. They hope to implement some major improvements come 1.21 and maintain compatibility with Forge mods on 1.20.
Forge and NeoForge probably won't be a problem since they're designing it to be fully compatible with old Forge and also pulled most developers away from old Forge in the process. Never heard of Quilt before though and can't find too much info on it, are there any big mods for it?