Is there a way to for the rate to 60HZ, to overcome this limitation of LibreELEC?
I assume your projector can only manage YCbCr 4:2:0 / 8 bit at 4K 60Hz. That HDMI mode (YCbCr 4:2:0 50/60Hz) is not supported by the Intel Xorg driver.
Try this Kodi-GBM test build of LibreELEC. It does not use the Xorg stuff, so 60Hz should be usable.