The RSS or meal planning app? If it's the former I like Feeder. You can probably export and import all your feeds.
I think some of my favorites are LibreTorrent, Session, and NewPipe.
I am a big fan of open source engine recreations, even if I don't play them a ton, so DevilutionX and OpenMW are worth mentioning. I think Xash3D is also open source if you want to play Half Life on the go.
I think OpenRCT2 has an Android app but I haven't bothered figuring out how to set it up yet.