Mod.io has now fully replaced the steam workshop support.
Be sure to check things out! https://mod.io/g/mixuniverse
The steam workshop is now fully removed from the game and the workshop has been unlisted. All previously uploaded mixes on the workshop are backed up so if you happen to not have run the game since the previous universe update, feel free to reach out at https://www.mixuniverse.net/contact, join the discord or start steam discussion and I can try to find it and send it over.
Thanks folks! Keep on making cool vibes!