Hi ashlar,
Thanks for your interest! 😃
Unfortunately, my Optoma UHD50 projector does not support Dolby Vision, so I can't properly test Dolby Vision FEL.
However, I can confirm that 4K UHD playback works beautifully on my HP EliteDesk 705 G4 SFF with the new LibreELEC 13 build.
I tested King Kong in 4K yesterday, and the picture quality on my Optoma projector was absolutely stunning!
The projector correctly recognizes the UHD resolution. Although it supports HDR10, I haven't verified whether HDR10 was actually active during playback.
Hopefully, someone with a Dolby Vision-capable display can test FEL on the same hardware.