I only know German ones: senfcall.de or bbb.digitalcourage.de

the big ones out there are BigBlueButton and Jitsi. they have a lot of public instances, so you can easily check if they fit your needs.

Damm i read ABP … and was confused. Yeh sure ads are smoll brain! (Same as ABP)

ADS?

Matrix i guess, its a federated messaging protocoll. Flagship messenger app would be Element. Sending large files would depend on the server you are on.