Thanks to Termux I am now running Spacemacs from my Android smart phone, driven by an Atreus keyboard from http://Keyboard.io (any keyboard can be used of course, but the atreus is very portable)

I will write up how to use Spacemacs/ Emacs on Termux, but it's pretty straightforward (so long as you use the FDroid application to install Termux - don't use Termux from the Android store)

I have just installed Spacemacs on Termux, but haven't found any issues. I've been using Termux for a few weeks with Neovim (https://practical.li/neovim/termux/) and it it's quite responsive (the phone is a Google Pixel 2XL from around 2018). FDroid is just an install from the Play store and doesn't interfere with the rest of the Android OS.