I would like to install the Nextcloud Android Client on my old tablet with Android 5, but i don’t know where to download the official version because on F-Droid is only a version which supports Android 6.
On Github you can download all the apks that have been released since 2016…
But I have no idea if it ever was compatible with Android 5 and if so up to which version.
You can enable
F-Droid Archive in the package sources of your F-Droid apps settings.
This will take a bit longer to update all apps meta data, but will enable you to install old stuff from ages ago.