My phone have f-droid client installed since many years ago (sorry for my bad English). I remember f-droid client used to allow user to downgrade installed app.
But until recently I notice that under an app’s versions list, there are no “Install” buttons any more if the version is older than installed version. The “Install/Upgrade” buttons only appears if version is newer than installed version.
From what time did f-droid client decided to forbid user to downgrade app?