When I click share in Jitsi (or whatever) on KDE 6.1 w/ Wayland in Chromium, I get offered to share the 'Entire Screen". After that dialog another one pops up with the options 'Full Workspace', 'New Virtual Output', 'Rectangular Region' and a list of my displays. 'Rectangular Region' allows to share a selected part of the screen, 'New Virtual Output' instantly creates a virtual screen, visible in KDE 'Display Configuration' that may or may not be positioned on top of pre-existing physical displays.
My personal feeling is, there are more modems that do not work under Linux than those that do. Or are detected but happen to randomly stop working during the day.