Consider using F-Droid reproducible builds and signing the F-Droid app with your own keys.

[pingu-the-penguin]

https://f-droid.org/docs/Reproducible_Builds/

[pynicolas]

Thanks for the suggestion.
When publishing the app on F-Droid, I chose to let F-Droid sign with their own key because I trust them more than me to keep the signing key safe.
Now, switching to reproducible builds would mean that existing users would have to uninstall the app and re-install.
And it's not clear to me what would be the advantage of switching to reproducible builds.