so the invitation is currently sent by email by the platform, but I suppose that's immaterial: it could be sent by any party, and it didn't have to be an email, it could (also) be a post to the chat group. I don't think it has a feature to post a reminder for a recurring meeting, though; maybe that's what you were looking for?

another point I don't get is whether you want the platform to reject participants outside of the scheduled meeting time. ISTM that ensuring the platform is there at the desired time is what it takes, and if it is available at other times, I don't see how that would hurt. but I'm not the one setting the requirements, I'm just trying to understand them to see whether GNU Jami would fit the bill for you. but really the only way to tell for sure would be by your giving it a try.

the one concern I would raise is that I don't know how big the meetings are. I haven't been to big meetings on Jami, and though it has worked superbly for 1:1 meetings even with my very old and slow and low-bandwidth computer (where no other chat system did), meeting 3 or 4 people at once was more than it (the computer) could endure. even more powerful computers may face trouble with very large meetings on Jami, though, because IIUC the party that initiates the group call becomes the one who receives the audio (and video) feeds from everyone else, and passes it on to everyone else.

so very large groups in GNU Jami could be as problematic as a very underpowered Jitsi server