'"It's not just you: Flatpak flat-out doesn't work in the new Ubuntu 25.10 release," writes the blog OMG Ubuntu: While Flatpak itself can be installed using apt, trying to install Flatpaks with Flatpak from the command-line throws a "could not unmount revokefs-fuse filesystem" error, followed by "Child process exited with code 1". For those who've installed the Ubuntu 'Questing Quokka' and wanted to kit it out with their favourite software from Flathub, it's a frustrating road bump. AppArmor, the tool that enforces Ubuntu's security policies for apps, is causing the issue. According to the bug report on Launchpad, the AppArmor profile for fusermount3 lacks the privileges it needs to work properly in Ubuntu 25.10. Fusermount3 is a tool Flatpak relies on to mount and unmount filesystems... This is a bug and it is being worked on. Although there's no timeframe for a fix, it is marked as critical, so will be prioritised. The bug was reported in early September, but not fixed in time for this week's Ubuntu 25.10 release, reports Phoronix: Only [Friday] an updated AppArmor was pushed to the "questing-proposed" archive for testing. Since then... a number of users have reported that the updated AppArmor from the proposed archive will fix the Flatpak issues being observed. From all the reports so far it looks like that proposed update is in good shape for restoring Flatpak support on Ubuntu 25.10. The Ubuntu team is considering pushing out this update sooner than the typical seven day testing period given the severity of the issue. More details from WebProNews: Industry insiders point out that AppArmor, Ubuntu's mandatory access control system, was tightened in this release to enhance security... This isn't the first time AppArmor has caused friction; similar issues plagued Telegram Flatpak apps in Ubuntu 24.04 LTS earlier this year, as noted in coverage from OMG Ubuntu.' -- source: https://news.slashdot.org/story/25/10/13/067256 Cheers, Peter