Prior to 17.10.1 it worked fine, but later drivers show that freesync is not supported.
This has not changed even at 17.11.2.
With 17.10.2 and later drivers, Stellaris(Stellaris on Steam Ver 1.8.3) will not start up, if it is 17.10.1 or earlier it is WHQL 17.9.3.
Do not proceed from where you pushed the start regardless of window, full screen, resolution.
Graphics RX Vega 64
OS Windows10 FCU
Driver Radeon Software Crimson Edition 17.10.2～17.11.2
Display JAPANNEXT JN-IPS2700UHD DP connect (http://japannext.net/?page_id=5056 )
M/B ASUS X99 DELUXE BIOS 3802
CPU i7 5960X
PS Corsair HX1000i 1000W
Adrenalin Edition 17.12.1 freesync supported !
But stellaris can not start ...