All I have to do to out-compete your app on f-droid is to update more often than you, even if I make no actual changes. Anytime anyone in your target category updates, you push out a version bump and you're on top of the list. Bonus points if you start your app name with AA0 so it's always at the top of both available sort orders.

"Recently updated" is a bad metric that does not help users. By offering no other sort options, and sufficiently motivated person can trivially dominate any category in the repo.

A recently updated app is not better than a less frequently updated one just by merit of a higher version number.