Name: Transmission (GTK)
License: GPL-2 or GPL-3
Upstream has been contacted: https://github.com/transmission/transmission/issues/64
I created this Flatpak before Flathub existed because we needed a good, user-friendly BitTorrent client to be available to Endless OS users. Later I submitted it to Flathub.
I don’t have time to actively maintain this. Fortunately the rate of upstream releases is slow. But there are a couple of open issues including an update to the app runtime. Anyone interested in helping out?