Update. After a couple days of searching and tinkering I have discovered the following:
The TVheadend Server add-on available in LibreELEC OS was written by Team LibreELEC specifically for LibreELEC OS.
I managed to download the add-on and install it in Kodi on batocera.linux 29 but as the add-on was written specifically for LibreELEC OS it doesn’t seem to work in batocera “out of the box”.
Issue: Not able to connect to TVH server in Kodi/batocera via web browser in order to run initial setup. I suspect it may be just a matter of editing a few lines of code but I have no idea where to start.
For now, I will stick with my “dual boot” method with LibreELEC installed to HDD and batocera running on USB stick.