It seems F-droid version tries to download bootstrap-arm.zip from a folder which only contains bootstrap-aarch64.zip (https://nix-on-droid.unboiled.info/bootstrap-release-22.11)
https://github.com/ImranR98/Obtainium https://privsec.dev/posts/android/f-droid-security-issues/
1) F-droid has been around for a long time and it's proven to be well governed.
2) F-droid tells me if the software is still maintained, if it's a fork of another project, if the opensource software is using non open service as a backend, etc..