Which app store(s) do you feel has better security than F-Droid?
This not too old issue may show the level of concern you should expect from F-Droid developers, particularly given the way you are posing your questions and complaints:
Maybe @hans would at least give you credit for being concerned or interested…
This also not too old post should point you to some useful reading materials.
FYI, ClassyShark3xodus app, available in F-Droid shows md5 and sha2x checksums and signature info for installed apk’s.