Thank you to everyone for the feedback (both public and private), we’re very grateful for your help.
It seems to us that we’re experiencing even more issues with the AppImage packaging system than we were with the Snap system used before. AppImage works well on machines with a set of packages installed which we expect, but less well on anything else (which makes things difficult).
We’ve decided to push forwards with 1.8 R6 released via Snap, and leave the AppImage for the time being.
There is a release candidate of 1.8 R6 to try: Xibo for Linux v1.8 R6 release candidate