Several issues here:
On the website, the listing for an app never shows more versions than the last 3 versions. Why only 3? Is that a server storage space issue?
The 3 most recent versions are /not/ the most interesting versions. For example, Wire app version 3.53 was the last version that functions on AOS 5 & AOS 6. As the Wire project tries to force large numbers of people to throw away perfectly good hardware and buy new phones, version 3.53 is the most important version to preserve because it works for more users than any other version. This version is lost. There is no APK file for it. Since the latest version is always available on the Wire website, it’s actually less important than version 3.53 which is not served from anywhere. Wire has DoSd users running version 3.38. So those users are forced to upgrade. Yet 3.53 is unavailable, so the users are effectively denied access.
And worse, even if users give in to pressure & run out and buy a new phone, this is apparently the UX: Last android version is a piece of trash, everything is worst, almost unusable · Issue #3748 · wireapp/wire-android · GitHub
F-Droid should at least keep the latest app versions /for every AOS version/. The repo needs to get smarter about which versions are important.
This problem exacerbates a bug in the f-droid app. When searching for “Wire”, the app finds nothing because no versions kept in the repo are suitable. So search results leave the user hanging. We have to manually browse through many irrelevant hits. Wire should still appear in the search results but there should be an indicator to inform the user that no compatible versions are available. It would be useful as well if the user is informed about the last known compatible version so at least they know which version to look for out in the wild.