Mozilla is still in the process of rewriting Firefox on Android with a faster codebase and modern enhancements, but as with any overhaul project, sometimes it takes a while to bring back features that the previous version offered. The newest versions of Firefox Preview and Firefox Beta (the latter of which recently switched to Preview's codebase) re-introduce functionality that was already available on the old Firefox browser, but there are a few new changes as well.
Firefox Preview now supports adding web apps to your home screen, and displays a message when the current page can be added to the home screen. However, unlike how Chrome and Samsung Internet install web apps to the system app drawer (because they are generated APKs), Firefox simply adds them as home screen shortcuts. Offline support and push notifications work as expected, though.
This release also marks the return of Picture-in-Picture support for online video. Just like with Chrome (and classic Firefox), opening the home screen while a video is playing in full-screen moves the video into a floating window.
The last major improvement is that five more extensions are now supported: NoScript, HTTPS Everywhere, Privacy Badger, Dark Reader, and Search by Image. These appeared in the Nightly channel last month, but now they're available in the regular Preview and Beta apps. I do hope Mozilla eventually allows all extensions in the new Firefox, or at least allow non-partnered developers to submit add-ons, but many of the most popular options are already present.