I have this issue here (26.04.3 Flatpak). I didn’t create the Reddit post, but someone else had the exact issue one year ago. I installed the System Package (Fedora) and out of the box, everything seemed fine. This would imply that it only happens on Flatpak. But the System Package also has another version (older version) than the Flatpak.
I would like to find out what the issue is, in case it happens again in the future. Just using the System Package doesn’t seem like a fix. I would like to find out the cause of the issue.
Project Monitor output works. But Clip Monitor output shows only grey box.
If you move your cursor to the right side of the clip monitor, you should see a sidebar pop up. Click the magnifying glass icon then click the “Reset Zoom” icon.