Thanks a lot, @jdaviescoates for the reply and the advice regarding separate installations!
I also saw the activity apparently halted at the jitis-app repo, that's why I was asking. But judging from the cross-linked bbb-thread, there seems to be work still going on in the direction of this app, so this is good news.
However, here is a (possibly naive) thought (without any deeper understanding of the matter):
Since the main problem seems to be to get a TURN server running on the same instance as the other cloudron apps, and since a TURN-server is optional anyway, wouldn't it be possible to include the jitsi-meet app into the cloudron app repository without a TURN server and create an additional repository, say "cloudron_dedicated" or "cloudron_exclusive", with a collection of apps that can only be installed exclusively on a separate/dedicated server? This app repo could include, besides a TURN-server app, also BigBlueButton (which according to their docs also requires a dedicated server to run on) and possibly other apps as well. Does this make any sense?