[Nouveau] unstable refresh rate

[James]

I was going to buy a new cable and I came across this description:
 >Category 2 Certified HDMI wire supports resolutions up to 4Kx2K (UHD) 
@30 Hz

https://www.cnet.com/how-to/what-is-hdmi-2-0b/
> HDMI versions compared
> HDMI Version 	Max Resolution 	Max 4K Frame rate 	HDCP 2.2 	HDR 	WCG 	Hybrid Log Gamma 	Dynamic Metadata
> 1.4 	4K 	30Hz 	No 	No 	No 	No 	No
> 2.0 	4K 	60Hz 	Yes 	No 	No 	No 	No
> 2.0a 	4K 	60Hz 	Yes 	Yes 	Yes 	No 	No
> 2.0b 	4K 	60Hz 	Yes 	Yes 	Yes 	Yes 	No
> 2.1 	10K 	120Hz 	Yes 	Yes 	Yes 	Yes 	Yes 

"Category 2" implies HDMI 2 but the "Max 4K Frame rate" of 30Hz says it 
is HDMI-1.4.