After a strange unnamed window appeared on my desktop, I used

xprop to identify it and a search lead me to

xwaylandvideobridge.

From the man page of

xprop - property displayer for X

SUMMARY

The xprop utility is for displaying window and font properties in an X

server. One window or font is selected using the command line arguments

or possibly in the case of a window, by clicking on the desired window.

A list of properties is then given, possibly with formatting

information.

From GitHub KDE

/ xwaylandvideobridge

About

By design, X11 applications can't access window or screen contents

for wayland clients. This is fine in principle, but it breaks screen

sharing in tools like Discord, MS Teams, Skype, etc and more.

This tool allows us to share specific windows to X11 clients, but

within the control of the user at all times.

How to use

xwaylandvideobridge should autostart on login. It will run in the

background. Next time you try to share a window a prompt will appear.

The previously selected window should now be available for sharing. The

title will always be "Wayland to X11 bridge" no matter what window is

selected.

The system tray icon provides finer control.