OK, just for learning purposes, I've just created a 5.1 LPCM audio-only VIDEO_TS folder on a CD-RW with DVD-lab PRO, and tested it on my old LG DVD-player.
Sadly its firmware was designed to NOT SEE above 2 channels of uncompressed audio.
Also, the 5.1 analog outputs work only for AC3 streams.
I'm afraid there are
zero DVD-players that
actually have the right to carry the «DVD-VIDEO logo».