I remember reading that bosses just scale to the amount of players so my guess is solo is actually solo. This would make the solo or trio only decision even stranger…

Hope you were able to fix your Home Assistant. I just came to quickly recommend a way to easily backup your installation. https://github.com/sabeechen/hassio-google-drive-backup

You can still download and play it. It doesn’t get removed from your library.

About the matchmaking, I don’t know, sorry.