As I have written the file was an example!
And all build ways will only work out of the box for supported devices. You want build for an unsupported device, or? ?
For unsupported devices you have to finf the device, vendor and kernel sources for your own and add then via roomservice.xml to the eOS sources.
Here you can find some more informational about creation of roomservice.xml [HOWTO] Build /e/ without docker for non LineageOS supported devices