What are your specifications? And why doesn't Mozilla meet them? Could help narrow down options
Free and Open Source Software
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Raindrop.io has been really good to me. I pay for it, but it's dirt cheap ($2/m for me)
It has both folders & tags, daily backups, permanent offline copies of your bookmarks, reminders & notifications for read-later. A good API, and integrations with automation software, FOSS projects....etc
They have IFTTT support so you can store your own offline backups or bookmarks based on changes you make in raindrop....etc
The mobile app and browser extensions are great.
Overall 10/10 it's the only bookmark and read later manager I've actually liked that has all the convenience doo-dads, features, and self-control that I desire.
Edit: https://raindrop.io/
Wallabag is self hostable.
Have you tried Omnivore?
(Wallabag has apps, browser plugins, terminal clients, RSS, etc. Wallabag.it has a 14-day trial and doesn't cost that much.)
Just save the URL: using something like Markor on Android you can save a Quicknote and sync it using Syncthing. Doesn't save the article, but at least you have the URL on both devices. I did this for months before deciding to use Wallabag.