Comment 88 for bug 2046844

We have an update of the firefox profile coming that supports the /opt/firefox/firefox location used as the default install for the firefox downloaded directly from mozilla.org

If you are running firefox out of your home directory, that will not be directly supported and you will need to chose to do one of the following to fix the issue.

1. The recommended way is updating the firefox profile in /etc/apparmor.d/firefox by adding the location you have firefox installed, and then reloading the profile with sudo apparmor_parser -r /etc/apparmor.d/firefox.

2. You can disable user namespaces, this will keep firefox from trying to use them as part of ts sandbox https://lwn.net/Articles/673597/

3. the least recommended way to fix this is you can disable the finer grained user namespace restrictions as outlined in https://ubuntu.com/blog/ubuntu-23-10-restricted-unprivileged-user-namespaces