It's a per app thing. Developers need to support it sadly it causes some issues with layout that most developers don't want to deal with, so it's not that popular. It's especially an issue in the multiplatform apps that share codebase with iOS
Good job on releasing your project to the public!
Making FOSS because you are frustrated/horrified with permissions of the existing apps is something that I can truly relate to.
Most of the FOSS is something that someone built for themselves and released for other just because. Try not to hold grudges if someone is annoyed that suddenly they get spammed with request that they don't wanna deal with.
You can use one of the bunch of RSS feed readers to do that. I haven't use it for years (basically since I lost everything I had on Google reader) so I cannot recommend you any apps
It's a per app thing. Developers need to support it sadly it causes some issues with layout that most developers don't want to deal with, so it's not that popular. It's especially an issue in the multiplatform apps that share codebase with iOS