Gsync not activating on Linux X11 (OpenSUSE TW)

My specs are Nvidia GTX 1080 and Asus Rog PG348Q Gsync monitor
I am using the standard 550 Nvidia drivers and latest Retroarch 1.19.1 (5 November)
I am using Plasma X11 and Gnome X11

On Nvidia X Server settings I activated the following settings for Gsync:

Sync to vblank, allow flipping, enable Gsync & compatible, enable gsync & api indicators, use conformant texture clamping.

I also add this command

nvidia-settings --assign CurrentMetaMode="DP-2: nvidia-auto-select +0+0 {AllowGSYNCCompatible=On}"

Whenever I run an application, on the top left part of the monitor the message BLIT and VSYNC appear. On top right the message NORMAL.

I installed and tried MAME and Dosbox Staging and BLIT indicator is green, which means that Gsync works. I could verify it by testing the shadows in Samurai Shodown 2 and the coin menu of Mortal Kombat 1. The shadows flicker ultra fast.

However upon launching Retroarch, BLIT indicator is always red. VSYNC indicator is red or green, depending whether I have Vsync enabled in Retroarch.

The VRR/Gsync monitor sync option on Retroach does not make any difference. Driver is Vulkan but even if I switch to OpenGL Core it remains red. Tried Samurai Showdown 2 in Retroarch (MAME core) and shadows do not flicker as fast as in stand alone MAME

Can anyone confirm whether Gsync works with Retroarch on Linux distros?
Is there any extra step to activate Gsync?

Start by reproducing RetroArch on Linux X11 with the reported Nvidia GTX 1080, Gsync monitor, Vulkan and OpenGL Core drivers, then compare its BLIT and VSYNC indicators with standalone MAME and DOSBox Staging. Done means identifying whether RetroArch requires an additional configuration step or has a rendering issue that prevents Gsync activation.