Yes, that's true, but because Android uses a completely new/private windowing system, none of your Debian-based applications can access either the framebuffer o

Yes, that's true, but because Android uses a completely new/private windowing system, none of your Debian-based applications can access either the framebuffer or the windowing system, so you'd be completely limited to running CLI packages. The best this would really offer is the ability to run an SSH daemon on the phone that you could access from a remote system, although be careful to avoid the iPhone SSH / root password vulnerabilities...