I tested this again more carefully.
The TURN service does indeed get stopped after app restart because of stopUnusedServices, but PeerTube itself continues to work normally and the socket/WebRTC behavior seems fine.
So my earlier assumption was probably wrong: the TURN service stopping does not appear to be the cause of the PeerTube issue I saw before. That may have been a separate glitch.
So it seems TURN is currently unused in my setup, and Cloudron stopping it is expected with the new unused-services cleanup behavior.
Thanks for clarifying.