I can’t help with that as i don’t use Linux. Maybe a permission issue on /tmp?
Nope, that is an Electron issue as far as I know, because this is an appimage I cant mess with the bundled permissions.
See this in the bug tracker for more discussion about it.
i ran into the same problem. i wanted to upgrade my client 1.0.170 running on linux debian to the newest version 1.0.216. the upgrade was aborted with the chrome-sandbox error message. when i tried to change permission, there was no chrome-sandbox file (or folder?) in /tmp/.mount_JoplinM4WuUs/ (however lots of other folders/files…)