Export: yes. Import: yes.
Ads: no. Trackers: ?
Android: https://play.google.com/store/apps/details?id=de.luhmer.owncloudnewsreader
Cross-platform email client providing POP/IMAP support, robust filtering, multiple accounts, and chat. Extendable via add-ons with RSS/Atom, etc.
Other services which can't import/export feeds but are still interesting and open source.
TTRSS-Reader is a client application for the project 
Tiny Tiny RSS , a PHP-based online feedreader which runs on your own webspace. If you want to host your own feedreader, want a cross-device-solution and don't want to use...
Feedbin is a modern web reader to follow websites, Twitter feeds and email newsletters in one place. It boasts a clean interface, is ad-free, and costs $5/month.
Rivulet is a simple way to get content in one place from all over the web. Like Google Reader, it loads web feeds (RSS and Atom) and displays them to the user. But, Rivulet is simpler and easier to use.
An open source RSS news reader to help you discover, track and manage only the content you care about. Getting better every week and made with ? in NYC.
Displays a sidebar that lets you manage your RSS feeds in a folder tree view in Firefox 57+. A "Legacy" theme is available to have look close to "Sage".
