A very quick update. The work I've been doing has suddenly turned in to 12 patches.
The TUF RGB patch series recieved some extensive and very good reviewing, so I think it is in excellent shape now.
TUF RGB patch series (includes a dGPU-only mode patch for a rare and specific kind of laptop)
Each of those links has the patches + cover letters and commit messages.
If all goes well, this work should hit Kernel 6.0