It should be released as v3.1.2: Android pre-release v3.1 is now available (Updated 10/08/2024) - #2 by laurent
Edit: Be aware that v3.1.2 is a pre-release — the latest stable version of Joplin for Android should be a 3.0.x release (see the release calendar). F-Droid seems to be publishing pre-release versions of Joplin.
Edit 3: Removed inaccurate information -- the latest Android version is v3.0.9 and not v3.0.7. GitHub issue.