What do you want to achieve? Keep it simple and clear!
Apeirophobia has an interesting lobby system where instead of walking into physical lobbies, you can use a UI lobby system where you can create/delete a party, and you can set whether you want the party to be public or private (which means players will have to use a code like 1234 to enter the lobby instead).
What solutions have you tried so far? Did you look for solutions on the Developer Hub?
I have looked for solutions on the internet and the Developer Hub to no avail. Am I not looking for the right systems? Are there kits/videos/posts that match what I want to achieve? If not, how should I go about making this? Any and all help is appreciated.
Doing everything inside GUIs and simply not having Characters loaded and moving around in the world is simple – just turn off Players.CharacterAutoLoads.
The grouping system is more complex, of course, but the difficulty is mostly just from letting it work across multiple lobby instances (as opposed to requiring everyone to be in the same instance to join a group).
If you don’t care about that, it’s dead simple to just have the Server keep track of which groups are active in a particular lobby instance in a Table of some kind and tell the Clients to generate a list of buttons to join them with or without a password input as relevant.