[Serious] Ubuntu 24.04: Firefox in snap with KeePassXC addon does not connect to KeePassXC AppImage

[benbucksch]

Opposite of #2176 (which is about non-snap)
Since I upgraded to Ubuntu 24.04, the KeePassXC Firefox addon can no longer connect to the KeePassXC Linux app. All attemps to connect fail. Therefore, I cannot use my passkeys to authenticate.

Expected Behavior

• Addon connects to KeePassXC
• Passkeys work

Current Behavior

• Connection fails. Constantly shows an error and [Reload]
• Passkeys are unusable

Possible Solution

Options:

• Let KeyPassXC (Linux app, with user permissions) modify the AppArmor rules to allow the connection
• Work with Ubuntu Firefox snaps maintainer to allow the connection
• In the meantime: Instead of an error message in the addon, detect the problem and show clear instructions what the user should do. (This is not a fix for this bug, but only a hotfix, a temporary workaround until it's fixed properly.)

Steps to Reproduce (for bugs)

1. Start KeePassXC, enter password to unlock database
2. Ensure that settings have [x] Browser Integration turned on, and [x] Firefox is turned on.
   

Note: This dialog specifically says that browsers installed as snap are currently not supported. (I just noticed that while reporting the bug.) That is the bug. Given that Ubuntu 24.04 installs Firefox as snap (and there is no deb anymore), that means that the most popular browser in the most common Linux distro is not supported.

3. In Firefox, click the KeePassXC icon in the browser toolbar and click [Reload].

Debug info

KeePassXC - 2.7.9 (latest) as AppImage
KeePassXC-Browser - 1.9.3 (latest)
Operating system: Linux, Ubuntu 24.04
Browser: Firefox

[benbucksch]

Compare #1426 #1875 #1828
Please note the suggestions how to fix it, here in "Possible Solution".

[varjolintu]

Duplicate of #1828.