Emacs is available as an installable package in Termux, so yes, org works too. And besides that there are dedicated Orgmode apps, e.g Orgzly. But those dedicate

Emacs is available as an installable package in Termux, so yes, org works too. And besides that there are dedicated Orgmode apps, e.g Orgzly. But those dedicated apps aren't as flexible as a full blown emacs.