Brief 2.5 is the WebExtensions release series. Tagging and full-text search are still missing, but everything else should work. If something does not, please file bug reports or comment on existing ones.
Brief 2.5 can reuse data saved by Brief 2.4, but not by earlier versions. OPML export/import can be used otherwise.
Changes in minor versions:
2.5.9 supports subscribing to feeds from XML view in Firefox 64 (no preview yet; download can happen instead), hides the subscribe button for PDFs and source view, and drops unused localization-related data
2.5.8 fixes one more bug with feeds without entry IDs and provides better error messages when unable to open the database
2.5.7 fixes processing feeds without entry IDs, implements some migration corner cases and ensures that losing preferences does not drop your feed list anymore
2.5.6 migrates data to the "default" storage, fixes incorrect entry starring, integrates once again with Firefox feed preview and supports more website favicons
2.5.5 fixes bugs in tutorial, feed list and OPML import/export, and feed parsing (entry order, permalinks, feeds with duplicate URLs).
2.5.4 fixes bugs in favicon update, OPML export, starring/unstarring, Brief page and feed properties dialog.
2.5.3 greatly improves update performance.
2.5.2 does not count excluded feeds for the Brief button counter, keeps favicon if update fails and works around blank windows on Linux.
2.5.1 fixes item starring, Atom feeds with relative links and unexpected errors during feed update.