Yeah, now im at the point where i use the edid of my samsung tv with the integrated panel of a wyse aio thin client.
i only use the 50 and 60 hz settings (there are more like 24hz, 25hz, 48, etc).
it was just an experiment but it works!
(before, on windows i was able to force refresh rate to 50hz with "custom resolution utility (cru)" on the wyse integrated panel too.
BUT NOW libreelec gui/interface goes black or turns the screen off for a second when the machine "does smthg".
for example. display is on and when i then hit a key on the keyboard, display goes black for a second.
another example. display is on and when i then insert usb stick it goes off or turns black for a second.
Another 1, is the minute of the time changed and screen turned black for a second.
For me it looks that any kind of change on the libreelec interface causes a "screen resolution" change. 
BUT!!! when i playback a video file. screen remains ON till video is stopped.
Do you have a clue what happens?
Any way to fix this "screen off" bug?
I think this is the only last hing that prevents me from using it. 
The "News Scroller" (tagesschau24, video source is 720p@50fps) isnt good in the video but in real it runs completely smooth like on a 50hz tv.