[SandmanUT]

Instead of loading Legacy (1) I reloaded my full backup firmware and all display ports (DP & HDMI) and all cables play nice (enough) with all displays once again. I didn't go back to stock, the box had been running your script with openelec/chromeos dual boot for a long time already, just back to the legacy version that worked previously and now once again. I stuck with GalliomOS this time, since it was what I was live booting off of. But the revert back to the working version enabled dp and hdmi (mirroring) while Gallium was still on the stick, which it wouldn't do under the UEFI, so that you know.

your GalliumOS install on the USB stick was done with the legacy boot firmware, so it would not be expected to boot with the UEFI firmware. If you're moving from legacy to UEFI, you pretty much have to start fresh.

I didn't have a Gallium install previously, I just made a boot stick from Windows to test against SteamOS, as per your suggestion to test the hdmi/dp handshake issue with UEFI. The same stick would boot up with either firmware, just one had dp & hdmi swapping support and restart hang and one did not.

My box doesn't want to play nice with the UEFI firmware and that's why I reverted back to the previous backup config, as outlined over on your script page. The old, working OS was openelec with chrome in a dual (that was the backed up firmware). I'm just outlining what solved the issue (moving backward) so that you have all the info if you encounter this again.