It is kind of wild to admit, but the bottom of this article made me think about the fact that RSS readers can be local apps for the first time ever... I've always used hosted services and run my own Miniflux server. But a quick search revealed a nice native linux reader: https://gfeeds.gabmus.org/ .
On Android there's the open source Feeder from F-droid.
There's no rule that says a feed reader HAS to be a webapp.