This works great, but I have some observations/suggestions:
1) When I open all in new tabs, it also opens the home page (site URL) of the feed. Firefox's Live Bookmarks did not have this behaviour.
2) Under More Options, I just discovered today that I can set a custom symbol/emoji for the Unread and Read Status of a bookmark.
This feature should be highlighted in your description and in the changelog.
3) The default for the Read status is this, ✓, a black tick mark, which makes it quite hard to see at a glance.
I changed it to ✅ which I think looks much better. I think you should make it the default or at least suggest it as an option in the description of this addon.
4) When I changed the symbol for Read status, I had to Reload Live Bookmark, or restart Firefox for it to apply to all 10 feeds I have saved in a folder. Please apply the change instantly.
Thanks for this great addon!

Edit:
It would be very helpful if you could add an option called Open All Unread in Tabs, above Open All in Tabs!
Right now I have to Open All in Tabs, remember the oldest unread tab name, find it, then Close Tabs to the Right to be left with the newest blog posts I have not opened before.

Works like a charm, just like ex-firefox live bookmarks. You can export the xml from there and import in Livemarks, no hassle.

Phenomenal add-on: it does the job FF used to do and more - big thanks to the Devs of this add-on.

Worked with Firefox to get my RSS feeds back

Macht was es soll. Folder-Icons spezifisch je nach abonniertem Feed wären noch schön.

Firefox's Live Bookmarks rocks.
Now, Mozilla Foundation drops this feature :-(
Livemarks gives us exactly the same functionality with exactly the same user experience.

Does what it says on the tin; returns RSS Feed headlines to toolbar folders.

Could be more sync friendly (say, autocheck a specific folder's urls for feeds?) but not an issue for me personally.

Perpectly resurrects Firefox Live Bookmarks.

Does exactly what Live Bookmarks used to, and even better! Thank you to the Developer for bringing, and improving, this beloved functionality back from the brink of oblivion.

Ein perfekter Ersatz für die ab Version 64 entfallenen "Dynamischen Lesezeichen" im Firefox.
Die Datei Firefox feeds backup.opml kann importiert werden.

A pretty good replacement for the old built-in rss feed reader

You saved my life !
Outstanding addon after this very bad new to suppress RSS in Firefox.
Many thanx

great addon.... as for new version of ffox that erased built-in livemarks, this is very apreciated!!!

Works as advertised

Does an excellent job replacing the Live bookmarks feature that was cut from Firefox.