Termux is an android terminal with apt. It should be possible to build git-annex this way, and this would be a nice alternative (or perhaps replacement) for the git-annex.apk.
Looks like termux uses ubuntu to build, but cross-compiles for android, using bionic. So, ghc-android would still need to be used to build git-annex.
May be easier to build an appropriate .deb from the android git-annex binary, and add it to termux's sources.list?
Update: There's already an open issue in termux for this! https://github.com/termux/termux-packages/issues/420 --Joey
This would also help with tor support on android, since termux has a tor package. And would avoid needing to bundle other often out of date stuff with git-annex.apk.