Been playing WD:L a lot lately and man, I have to say, HDR is a bigger game changer than even ray tracing - and it's not even close. Switching between SDR & HDR is like when I switch between taking my glasses off and having my glasses on. I wish I could show people the difference but I'm not even exaggerating - I would upgrade the TV over even the GPU (unless it's iGPU), and over anything else. It matters THAT much, and keep in mind you can easily get 10 years of life out of a good TV. So no reason to skimp!
Granted, the downside is that not every game is HDR, nor is the HDR always that good, but going forward - that's the future of gaming. Very few AAA titles coming out with no HDR support.
You don't need to go crazy, just a decent fald TV is enough to get a good grip on HDR, and then you can choose between bigger or better.
Which TV to buy? This one is easier than you think.
Avoid Samsung (gimped game mode - even in 8K TVs) & LG lcds (worst quality ever). Sony is a safe buy overall even though it might be missing a feature or two depending on the model - it's super reliable. LG oleds are the best for gaming atm offering the best package but they're more expensive and burn-in is real (that should factor into your costs/benefits analysis; it's not going to happen as soon as you turn it on, but you'll not get more than 14000 hours without damage, at best).
Jump off for HDMI 2.1? Sony X900H/XH90 (its main flaw is that at 4K 120hz the actual image resolution isn't what it's supposed to be, so it's softer than 4K 60). Best HDMI 2.1 TV? LG oleds, either this year or last year, both are fine (B, C, E, G etc; 9 or X = 2019 or 2020)
If you're not worried about HDMI 2.1 too much and just want good HDR with 4K 60, then there's a much wider selection available, including last year's models like Sony X950G, or previous years' even X900F. The TCL 6 series 2020 is also a decent jumping in point (avoid all the others, for various reasons). Avoid Hisense, it's awful and has big problems with QA. Avoid Vizio, also awful QA and quality.
Considering how good & cheap the Sony X900H is though, it's hard not to recommend it as a blanket recommendation. For people with extra to spend tho, an LG oled will be great. Besides that there's really nothing else worth buying with a gaming focus in mind.