Because I’m in the Mac ecosystem, I use NetNewsWire on my devices and sync with iCloud. Before that, I used Feedly to sync. Feedly also has a web interface. I’m not sure what the best RSS apps are for Windows and Android are, though.

Here’s an article Wired did on feed readers last year. Many of them are subscription services, but some are freemium. (NetNewsWire is totally free).