Thanks @harvey186 @Anonyme. I was only building this in response to this thread, not for my own use, and because I have some unused credit with OVH. According to https://wiki.lineageos.org/devices/#motorola it is supported by Lineage so I thought it would be straight forward (the ROM for G7 river built with no problems).
I don’t think I want to spend the time tracking down the necessary files and creating the manifests so I will stop trying 
Thanks again for your help .