Flatpak apps mysteriously failing to launch

Finally figured out the mystery of intermittent apps failing to launch on my Fedora/KDE system. Every so often after a reboot, my browser and other apps, like Slack, seemed to stop launching. Usually rebooting seemed to fix the problem, so I never dug into it. The problem turned out to be /keybase — a FUSE (filesystem in userspace) mount left behind by Keybase. When the Keybase service crashes or…