In the category of "should be made available" here's some LucKey Productions titles that could be compiled for Android and are suitable for playing on mobile:

• heXon
• Open Saucer
• Quatter
• A-Mazing Urho
• Tux!
• Blip 'n Blup

I (main developer) however do not own a smartphone. Come aboard the Colourship if you'd like to help out!

BSD's Beastie is nonfree.

Beastie and Hexley are not free culture: https://libregamewiki.org/Talk:SuperTuxKart

Maybe have a look at the Toots, Carrot and Sepia karts I made: https://gitlab.com/luckeyproductions/goodies/stk-addons/-/tree/master/Karts