Here's what I'm doing at the moment.. and just know it's a sad workaround given that Oculus changed their experimental features with Family/app sharing. It used to be able to run 4 games at the same time, I was playing with my family and a friend so 4 oculus quest 2 devices. Before you could just have the main share the account and 3 others could play at the same time, it was the best, exactly what we were drawn to or believe the potential of family app sharing. They nerf (gave us a weaker version) of this feature so that the max you share an account and device at the same time would be "2".
Option 1: We wait for a potential update where they bring this feature back where you can share your main account to up to 3 other users that can also play at the same time, a very helpful budget feature for a family of 3-4. This is probably unlikely, in the end, it is probably all about $. That's the only thing that makes sense in terms of why they nerf such a great feature.
Option 2 (this is what I'm doing; requires only 1 Copy of the game): Continue to share your main library account games with other family member devices. In this example, I'll use Elven Assasin (EA) game. Device A (Main) turns on APP sharing in settings and logs on to Account B and starts EA. Account B, C and D all need to log on the main user account A. Now the problem lies that Devices B,C,D are all hopping on to Account A (main game profile) A all at the same time. So that's when you get "Multiple Devices Can't Access This App At The Same Time". The stupid workaround so far, is hitting the "oculus home right button" and it'll exit that pop-up. Depending on the game, the pop-up will come up potentially every 10 seconds - 2 minutes. It felt like EA it was popping up every 2 minutes but all 4 of us were able to play together at the same time.
Option 3: (requires 2 copies of the game) Using EA as the example again.
Main Device A enables APP sharing and then logs onto Account B. Therefore Device A has access to EA and can play while on Account B. Device B logs onto account A and launch EA to play the same game as Device A.
*** Device C another main user, has bought the game and turn on APP sharing. Device C logs onto account D while launching EA. Device D hops onto Account C (2nd main), and can play at the same time with Device C but in addition also devices A and B as well.
I hope that makes sense, so far option 3 is what seems to be the only way without glitching pop-up errors unless they decide to nerf or buff this app/family sharing feature again. It's definitely a cheap power move on the developer's end. I have yet to buy 2 copies of every game for my family because that's insane. Maybe when certain 4+ player co-op/multi-games are in a bundle sale I'll consider it. But for now, option 2 of hitting the oculus home button is one way to play together with 1 purchase at the price of hitting that home button very often.
I hope that helps.