Which version of HDMI cable comes with the ONE X?

The cable labled version is not that important over a short run. Its the chipset inside the device and the display thats important.

VRR on LG SM90 also works via HDMI 2.0 cable. If so, i really do not need a 2.1 cable.

The cable labled version is not that important over a short run. Its the chipset inside the device and the display thats important.

Mini-HDMI is just the regular HDMI pinout in smaller form factor. Strange that your monitor uses mini-HDMI, but you don't need a special adapter. You would just need to get an HDMI-to-mini HDMI cable. For a monitor of that caliber (and price), it had better
at least come with one of these cables!

You also mentioned it's HDMI is version 2.0. HDMI 2.0 is the required version for the Xbox One S/X to output 4K@60Hz with HDR, so it
should display without a problem. The things you read about some monitors only supporting up to 4K@30Hz is because their HDMI ports are version 1.4.

I think the issue maybe 1 which xbox your using if your on a one x it maybe the version of hdmi cable you are using and the converter may not support 4k hdr my friend.

I feel I need to correct some information here.

HDMI cables don't need to be 'gold plated to support 4K

There're no such thing as 1.4 HDMI cable or 2.0 cable.

HDMI cables are dumb, they don't have versions, only the interface has versions.

Basically, any HDMI cable - even the dirt cheap ones -should be good enough for 4K60. The Xbox One X HDMI isn't gold plated.

4K HDMI cables are nonsense