Windows (cross-platform): GitHub I’m not listing links for all 6-ish platforms of just this one individually just go here.
The aforementioned are readers which can either read feeds saved in them locally, or on a supported service. If you wish to self-host a feed aggregator (so you can sync your read articles etc across platforms), I recommend FreshRSS.
NetNewsWire can sync this stuff over iCloud.
Thought I’d drop my Reader recommendations (all free of cost and FOSS):
The aforementioned are readers which can either read feeds saved in them locally, or on a supported service. If you wish to self-host a feed aggregator (so you can sync your read articles etc across platforms), I recommend FreshRSS. NetNewsWire can sync this stuff over iCloud.