Not all Linux distributions which support apparmor come with profiles for Firefox or Thunderbird. I copied the profiles from Ubuntu's packages and modified them slightly to make them work for my environment. You're welcome to make use of them as well.
The firefox-esr profile is for Debian 10/11. Run sudo touch /etc/apparmor.d/local/usr.bin.firefox-esr first, then copy usr.bin.firefox-esr to /etc/apparmor.d/ and activate the profile.
The firefox profile was tested with Manjaro Linux. I've added support for KeePassXC extension, Yubikeys and widevine video plugin.
Copy firefox to /etc/apparmor.d/abstractions/ubuntu-browsers.d/ and usr.bin.firefox to /etc/apparmor.d/. Also run sudo touch /etc/apparmor.d/local/usr.bin.firefox, then activate the profile.
The thunderbird profile was tested with Manjaro Linux. Run sudo touch /etc/apparmor.d/local/usr.bin.thunderbird and copy usr.bin.thunderbird to /etc/apparmor.d/ before activating the profile.