No, there's no tab grouping on Firefox for Android. I have not found an extension that works for mobile for that functionality either.
Firefox
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Firefox on mobile does have something called Collections. It's not a tab group, but like a group of bookmarks you can save.
I wish, one of the features I miss from Chrome.
Maybe Fennec (a Firefox fork that lets you install desktop add-ons) and this https://addons.mozilla.org/en-US/firefox/addon/simple-tab-groups/.
Hold on, you can install desktop add-ons on Fennec? How can I accomplish that? I only ever found the officially supportet add-ons like uBlock and PrivacyBadger.
Custom Collection https://support.mozilla.org/en-US/kb/how-use-collections-addonsmozillaorg
This works in Beta, Nightly, and all the forks (iirc).
Awesome, I didn't know that. Thanks for sharing!
Personally, I use the Mull fork of Firefox - wonder if it works for that as well. I don't feel a need to have 1:1 functionality on my phone and computer so I haven't gone down that path yet, but now this conversation has me pondering it.
With recent beta, besides creating a custom collection, you can now install directly from extensions pages. You may have to toggle desktop to make it works.