someone provided instructions how to manually download and install java 17 from zulu on debian buster.
Upgrade OH3 to OH4 - Setup, Configuration and Use / Migration - openHAB Community
i have done it and it works, I am now running OH 4.0.2. on debian buster raspbian.
so now I can fix all the issues, make it stable, and then do openhab-cli backup, and restore that backup on a fresh openhabian machine.