I did something similar for myself. It should work the same for a group of steam friends if the data is the same (which I guess it is if you're using a steam sensor for each one of them).
I'll just say up-front that this is a lot of setup to get this to happen. But it shouldn't! I plan to make this into a custom HACS card since just getting all this data directly from the steam sensor will be much easier with a custom card. I'll keep you posted when that happens, but I hope this will get you what you want in the meanwhile :slight_smile:
My setup shows the following things (see image for reference):
- my steam entity without a now playing section when I'm not playing a game
- a "now playing" section once I start playing a game
- an hassio notification when I start playing a game