Not saying it’s perfect, but I just posted my steps to get nextcloud on a DL4100 (WD MyCloud Device)
It seems to be working thus far, using wonderfall’s docker image.
https://community.wd.com/t/nextcloud-install-instructions-attached/190470/2
Hopefully this will help someone. Feel free to critique or offer improvements!
@robclay good to see you progress on this. I had put aside this project to get to it later. I was after creating a bootable usb with an automatic installer of Ubuntu Server with LEMP Stack and the latest NextCloud that I could simply plug in the back of my WD MyCloud 2TB NAS (Model WDBCTL0020HWT-EESN) and let it do the job by itself.