@pvchandler glad it worked for you!
To get the grabber running on a non-LE system...I think the key is determining where to install the grabber file and making sure it is executable. Do a search on the ubuntu system for the tv_grab_zap2xml file. If it is installed in the appropriate kodi addon folder it is likely just an issue with permissions. Check to see if the file is executable. If not, use the chmod +x command to make the file executable. Then reboot and see if the grabber shows up in tvheadend.
Thanks for the quick reply!
Searching (Nautilus) for hidden files/folders from any given point (CTRL-H) shows...
On the known good LibreELEC 7.0.3/USB drive, find: /media/paul/Storage/.kodi/addons/script.module.zap2xml/bin/tv_grab_zap2xml. Looking at permissions here, under 'owner' and 'group' it shows 'root' and the check mark for 'Execute'.
On the Ubuntu 16.04LTS Desktop, find: /home/paul/.kodi/addons/script.module.zap2xml/bin/tv_grab_zap2xml. Location is probably correct, and permissions show Owner as Me, and Group as Paul; all 'Read and write' and I was able to simply click the box for the check mark (Execute: x Allow executing file as a program). I believe that this check box is the same as 'chmod +x'.
TVHeadEnd still not pulling in the new module.
Two guesses here: either file needs to be changed to 'root' (I don't know how to to that) or these 32 other XMLTV listings are interfering (unknown how they got there or how to delete.)
Another offshoot idea I've had (might try tomorrow) is to create a new USB drive for that 'Desktop/server' computer; bootable running LibreElec, and share drives/files from there via its internal Samba, then having the laptops point there for shared files and TV stream. In other words, I'm not demanding that that computer run Ubuntu as it currently is. Thanks again,
Paul.