This is the problem with assuming, there’s nothing in their notes about having a second monitor connected at the same time as the one that is tearing. This possibility didn’t even occur to me, but it’s plausible.
edit: literally a minute after I reply, OP confirms you are correct in your assumption.



It wasn’t at all clear that you had a 2nd monitor connected, that is also useful information. Still, not enough data to really know.
Are both monitors the same make and model? If not, then it seems likely there’s an issue with your GPU or HDMI cable, but the symptoms are different because the monitors are manufactured by different companies. If the monitors are identical to each other, then we’re back to most likely being an issue with the 1st monitor.