Custom Supported Hardware

[1ubuntuuser]

Hello, is there any documentation or recomendations for adding support for a device not on the list? Looking at using this for my own hardware build. Probably use an off the shelf arm SBC and add additional hardware too it.

Is it fairly straight forward provided the device supports android?

[1ubuntuuser]

I found this, but it is 7 years old. Is it still relevant?
https://github.com/omnirom/Docs/blob/master/Porting_Omni_To_Your_Device.md