Mod Nokia 800Tough recovery

[mahz...@gmail.com]

I am trying to mod the recovery of my Nokia 800Tough.
My goal is:
* get adb working in recovery mode
* hack the recovery to install unsigned zips
* change the label from KaiOS recovery to SkyOS Recovery (SkyOS is my custom ROM for this device)
After a lot of work, mistakes, I was able to edit the recovery using a combination of these two guides:

https://wiki.bananahackers.net/root/recovery-mode

https://github.com/minhduc-bui1/nokia-leo/wiki/6.-ROOT:-Boot-partition-modifying

I currently have 3 problems:
* ADB works only partially (adb pull/push works. adb shell returns a strange error
- exec '/sbin/adbdsh' failed: No such file or directory (2) -
* Although I replaced ramdisk/res/keys with test keys, as explained here I still can't install unsigned zips.
Maybe it's related to the problem presented here?
In any case, the solution offered there did not help me.

* I don't know how to change the caption that is displayed in recovery mode. Does anyone know how?.