As recently you can no longer add groups as collaborator in the game settings permissions.
When you try to add a group to it, it will only show users.
Whatever group you try to search, it will always show usernames instead.
I don’t know when this bug started happening as I don’t often use this feature. But I can confirm it’s already from 08/02/2020 (Saturday) possible before.
Example of the bug, trying to search for “Fros Studio”:
https://gyazo.com/2491d8bc4c92a8837bfdc48ce99c09df
If the GIF doesn’t work, here’s a picture:
Edit: This also doesn’t work for non-group games to add groups as permission.