Thanks to StackOverflow, I now have a way to start my Termux Shell, even in ADB!

https://android.stackexchange.com/questions/225260/termux-running-termux-via-adb-without-any-direct-interaction-with-the-device

Installing ADB is very trivial, so being able to access my own shell from virtually any device, with or without network, is really amazing.

I also compiled dinit https://github.com/davmac314/dinit on the device itself; so together with Termux:Boot, I can have a tiny init system ready to go to launch my SSH server on boot and what not.

Last thing: Figuring out a way to run commands on login and logout in Fish... so I can do termux-wake-lock and termux-wake-unlock on login and logout respectively.