Error running AppImage "fusermount: mount failed: Operation not permitted" on Ubuntu 20.04
Solution 1:
On Ubuntu 20.04, completely reinstalling fuse helps.
Either with:
sudo apt-get remove --auto-remove fuse
sudo apt-get install fuse
or less intrusive
sudo apt --reinstall install fuse
Source information: https://youtrack.jetbrains.com/issue/TBX-3544