Yeah, screensharing is not a thing in most clients, but I think it's a matter of time (years?) before it's properly implemented. In the meantime, you can use jitsi meet? Not sure if it covers your use case. I'll just copy this reddit comment, which has some good info:

Yes, it’s possible, but with some limitations. For video calls between a Linux and a Windows client using ejabberd, you need an XMPP client that supports WebRTC. Some options: • Dino (Linux) – Supports video calls but no screen sharing. • Gajim (Linux/Windows) – Can do video calls with plugins, but no screen sharing. • Jitsi (XMPP mode) – Supports WebRTC and screen sharing but requires a separate Jitsi server. Since most XMPP clients don’t natively support screen sharing, you have two main options: 1. Use Jitsi Meet, which integrates with XMPP and allows both video calls and screen sharing. 2. Use OBS VirtualCam (on Windows) to share the screen as a “camera” in a video call. If you want a fully functional setup with both video calls and screen sharing, setting up Jitsi Meet with ejabberd is the best approach.