Similar to NetNewsWire on macOS, NewsFlash is a clean, stable, fast, free, no-clutter and no-nonsense RSS/Atom newsfeed reader for Linux. You can read articles in the application or open them in the web browser of your choice. It syncs new posts quickly and I haven’t had any issues with it getting stuck the way I had with Communique (before the latter stopped working entirely!)
It’s an app, not a service, so it’s not tracking you or inserting ads. That also means there’s no web version. But it can sync over several web-based newsreaders like FreshRSS, Nextcloud News (which is what I use it with), Inoreader and more. So you can keep track of your subscriptions and read/unread articles across devices. But you can only connect it to one service at a time. Note: With Nextcloud, syncing may be faster with an app-specific password.
You can set up multiple external actions including sharing to Pocket/Instapaper, Mastodon/Twitter, Reddit and Telegram, plus one custom URL-based share. I’m using it to connect to my Postmarks instance for public bookmarking.
NewsFlash is an entirely rewritten application by the author of the now-discontinued FeedReader, who describes it as the “spiritual successor” to the older application.
Built in GTK for GNOME, but I’ve got the Flatpak working just fine on KDE Plasma and LxQt too.