I can’t say anything about this functionality in Chatty (as the default SMS and Matrix client on the Librem 5). But I’m currently working on live video chats within the GNUnet Messenger application to get it working on the Librem 5 besides other devices.
So from my perspective there’s still a lack of API integration (at least in Byzantium) when it comes to accessing the cameras using pipewire and libportal. I hope this changes with PureOS Crimson, so a lot of apps should be able to capture or stream from the camera, allowing video chats to get working.
It’s also a little tricky on the Librem 5 since it doesn’t support hardware accelerated video encoding. So you either run into CPU limitations or reduce the resolution quite a bit. Don’t expect high quality is all I gonna say but I think that’s usually fine. Decoding video streams is not an issue.
I’d also like to add that sending video files should already be possible using apps like Element, Signal, Telegram and others.