what is the standard editor in Android?
As mentioned, I would be happy with sed.
Still as later mentioned in a comment, I am in a virtual environment, so no trouble dropping one OS and start using the newer one.

Apparently, my problem was staying in Android 5.1.  Starting version 6 Android includes ToyBox, a rather limited alternative to BusyBox, legally compatible with the non-free license of Android.

The ToyBox hint comes from the author of droidvim.