Firefox mobile has tabs. You can even have tabs in normal mode and other tabs in incognito mode.
Firefox mobile has tabs, though?
On tablets (and possibly large phones as well depending on your dpi settings), the pre-rewrite version had an actual tab interface similar to Desktop Firefox.
Have you possibly installed Firefox Focus mistakenly? I purposely use this version to force myself to stop hoarding tabs, at least on mobile devices. It sounds as though the main version of mobile Firefox has tabs.