The upgrade button doesn't do anything.

This is intended as the f-droid support was not requested by app developer and supporting app in F-droid would need some serious work

@GeoZac how do I get the premium version, then? Without having to compile from source. I'd really like the black AMOLED theme. Maybe just upload the premium version to F-Droid and people who want to donate can just send money to a Bitcoin address / PayPal or something?

The apk at f-droid is an automated build from the tags here at this repo. Like I said, offering pro version at f-droid would need some serious work . That being said currently there's no way to get premium version, unless purchased from PlayStore

PS: Too bad we're speaking this at the midst of "Hacktoberfest",but sadly that's the state of open-source