Don't expect Firefox for Android to get tablet UI anytime soon
www.androidauthority.com
Mozilla has confirmed that optimized tablet UI is not a priority for the Firefox on Android team and that it is focused on other matters.

TL;DR (From Android Authority)
• Mozilla responded to a review mentioning the lack of tablet UI optimization for Firefox on Android.
• Mozilla confirmed that its team is not working on optimizing the tablet experience at the moment.
• Mozilla did, however, say that it hopes to revisit tablet optimization when time and resources permit.

            • Possibly linuxEnglish
              1·
              10 months ago

              Its the Linux version. You need to setup Termux with a Linux desktop for it to work. As I recall the ESR version was the only one that worked properly. This was 4 years ago now so it may not work.

              Just a side note, if you do install Termux make sure you install it from F-droid. The Termux from the play store is missing functionality and tends to ddos the repos. It also isn’t really maintained.