Specifically: https://play.google.com/store/apps/details?id=org.mozilla.fe...
"Firefox Preview marks a release of the early version for an experimental Firefox browser for Android. Built on GeckoView, Firefox Preview is a pilot for early adopters, developers, and anyone who wants to help make a better, more private Firefox for Android."
If you like Firefox I'd give it a go. I've never been a fan of the normal Firefox mobile app, but recently switched back from Chrome so I think it's a nice alternative.
Add a bookmark via overflow (three dots) then star at the bottom.
Access your bookmarks via overflow (three dots) -> Your Library.
I'm not really clear why it has both bookmarks and collections.
Edit: how to add a bookmark changed from the bottom shelf to the overflow menu with today's update
https://github.com/mozilla-mobile/fenix/issues/574#issuecomm...