Besides last-minute breakage with some executables over the switch to Rust Coreutils, Ubuntu 25.10 ended up shipping with broken Flatpak support.
Reported in early September but not fixed in time for the Ubuntu 25.10 release this week was errors when trying to install Flatpaks. The issue was found last month to be an issue with AppArmor and specifically its fusermount3 profile. Workarounds have been available but nothing fixed properly in time for the Ubuntu 25.10 release day. From Canonical’s perspective, Snaps are their preferred format for sandboxed apps on Ubuntu Linux.
Only yesterday an updated AppArmor was pushed to the “questing-proposed” archive for testing. Since then over the past day 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.
Those curious about this broken Flatpak support on Ubuntu 25.10 can track this Launchpad bug report for all the details and available workarounds or for those wanting to test it from the proposed archive.
