The new Ubuntu 25.10 release suffers from a significant issue: Flatpak installations are failing. Users encounter an error message related to unmounting the revokefs-fuse filesystem. This problem hinders users from installing their preferred software from Flathub. The root cause is identified as AppArmor, Ubuntu's security tool, lacking the necessary permissions. Specifically, the AppArmor profile for "fusermount3" is causing the conflict. This bug has been reported on Launchpad and is being actively addressed. The issue was reported early on but wasn't resolved before the 25.10 release. A corrected AppArmor update is now available in a testing archive. Numerous users have reported that the updated AppArmor resolves the Flatpak issues. The Ubuntu team is considering an expedited release of the fix. This is not the first time AppArmor has caused issues with Flatpak, as evidenced by previous problems with Telegram.