Tested RX 550 with 4k@120 TV and 1080p@240 HDMI monitor

Author: TheStalwart

db/AMD/2017 RX 550.yaml

@@ -1,18 +1,45 @@
 gpu: Radeon RX 550
 modes:
+- connector: HDMI
+  resolution: 4k@60
+  bits: 8-bit with dithering
+  color: YCbCr444
+  hdr: true
+  vrr: false
+  supported: true
+  notes: Enabling HDR downgrades bit depth and disables FreeSync. Samsung QN75C reports both HDR and VRR enabled but games with unsteady frame rate experience visible tearing
+
+- connector: HDMI
+  resolution: 4k@60
+  bits: 8
+  color: YCbCr444
+  hdr: false
+  vrr: true
+  supported: true
+  notes: FreeSync only works if HDR is disabled in Windows Settings. Verified in Serious Sam Fusion on Samsung QN75C - with HDR off and settings cranked TV reports refresh rate floating at 45-55
+
 - connector: HDMI
   resolution: 1440p@144
   bits: 8
   color: RGB
   hdr: false
   vrr: true
   supported: true
-  notes: HDR toggle switch is available but cannot be enabled
+  notes: HDR toggle switch is available but cannot be enabled on LG 27GN800
+
+- connector: HDMI
+  resolution: 1080p@240
+  bits: 8
+  color: RGB
+  hdr: false
+  vrr: true
+  supported: true
+
 - connector: DP
   resolution: 1440p@144
   bits: 10
   color: RGB
   hdr: false
   vrr: true
   supported: true
-  notes: HDR toggle switch is available but cannot be enabled
+  notes: HDR toggle switch is available but cannot be enabled on LG 27GN800