I discovered a while back when I was downloading a new Emacs source tarball from the GNU ftp server that there was an .apk. Out of curiosity, I downloaded it to my phone, installed it, started it, and thought, "Oh that's neat!" Then I promptly closed it and forgot about it. Until just a few days ago.
I was on Mastodon and ran across a discussion about Emacs on Android. There were actually people using Emacs on Android successfully. The pivotal discovery was an on-screen keyboard called Unexpected Keyboard, which was originally designed for people using Termux on Android. At first glance, this keyboard appears almost unusable, but with the brief tutorial and a little practice, it's really pretty awesome. And it's kinda what makes Emacs on Android usable.