Despite what vendors would have you believe, there is no such thing as a “1.4” or "2.0” HDMI cable. There are only three official levels of HDMI cable: “Standard”, “High-Speed”, and “Premium High-Speed”. Standard cables are guaranteed up to 1080i/60; High-Speed is guaranteed up to 4K/30; Premium High-Speed is guaranteed up to 4K60 10-bit.
(EDIT: HDMI 2.1 actually is a whole new standard beyond those, but if a cable is advertised as HDMI 2.1 at the moment, that’s quite likely a lie, unless it’s a specialist, high-end thing).
Plenty of cables work okay well beyond what they’re officially certified to. Amazon Basics cables, for example, are not certified as Premium High-Speed, but do generally work at that level anyway - the certification process costs money, which Amazon doesn’t wish to pay; Blue Jeans Cable series 1-E cables are about as high-spec as you can get, but aren’t certified as Premium High Speed, either, despite exceeding the electrical requirements at most lengths - the Premium High-Speed standard also requires a certain level of mechanical flexibility, and they’re too rigid.
But you can tell a cable that is certified as Premium High-Speed, because it will be supplied with a bar code you can scan (that will take you to the certifier’s website and the entry for that cable). Any advertising pictures for a Premium High-Speed cable will generally have the bar code in the photo as well.
As the Dude says “Yeah, well, you know, that’s just, like, your opinion, man!”
As I said above, the fact that a cable isn’t certified as Premium High Speed certainly doesn’t mean it won’t work at 18Gbps - it may well; but nowadays I never use a cable that isn’t certified, because it’s simply not worth the potential hassle. Any kind of problem with any video device, and the first thing a manufacturer will ask you is if you’re using a certified cable; if you aren’t, they’ll refuse to offer any other support until you are.
And some devices exceed the HDMI spec, while others are only barely within it, meaning that the same cable will work perfectly with some devices but not with others. My TV is a bit finicky compared to some.
Most expensive cables are a rip-off; but you can get a certified cable on Amazon for about £8 (for a short one), and at that sort of price I can’t see any reason to take chances.