A number of non-v1-maintained boards come across the list. If it were me, I find a version of Marlin for my board/display combination. Often you will find a gitHub project for a specific board provided by the manufacture of the board. After you have some version of Marlin running on the board, I’d pick a V1 maintained firmware that was the closest to the board I have purchased, and I’d run a diff between the configuration.h and configuration_Adv.h of the two versions of the firmware. I’m using Meld these days to run software diffs.
The things you need to address are relatively small. Off the top of my head:
- Stepper settings
- Display settings
- Endstop settings (only important for dual endstops)
- V1 Custom menu (optional)
- Laser settings (optional and only active for a couple of V1 maintained boards)
By starting with a firmware made for your board, you get the first three handled. For most boards (boards that have been integrated into the general Marlin build), selecting the Motherboard will percolate the other settings (like pins), that are needed for that board.
Note that within the last few months, lightly tested firmware for a few “non-standard” boards have made their way to the V1 release point, so that might be an alternate pathway.