Plasma developer David Edmundson demonstrates how a desktop using Wayland, Qt6 and KWin can recover from a catastrophic crash as if nothing had happened.
http://blog.davidedmundson.co.uk/blog/qt6_wayland_robustness/
You will lose no data, the video you were watching will not skip a frame, and the contents of your clipboard will remain intact.
If you can see your wallpaper, you don’t have enough windows open.