Looking at the EOTFs for the H8F and H9F, I'd say that works a lot better (but not perfect) on the H8F, which mostly has just black crush. The H9F has black crush and makes bright scenes too bright in a nonlinear fashion, first increasing it with a high slope, then going below linear to the max brightness. Brightness bump effectively adds an intercept, and contrast decreases the overall slope.The H8F also has black crush and contrast clipping in HDR. To alleviate this, I dropped Contrast down to 42 and bumped Brightness up to 54 (or 52 if using the default Contrast of 58). This alleviates black crush and clipping in HDR without raising the black level. If you go above Brightness of 54 with the Contrast set to 42 then you'll start raising the black level. I wouldn't touch Brightness with SDR as it seems to be fine. Again, this for the H8F. I have no experience with the H9F, so I don't know how well this would translate to that TV.
https://www.rtings.com/tv/tools/compare/hisense-h8f-vs-hisense-h9f/839/908?usage=7318&threshold=0.1#comparison_2411 (search for EOTF since their #linking is before images load for some reason)
Interesting, TCL, at least for their 8-series, heard the complaints and actually released a firmware that fixed it. Their 2019 6-Series is still worse than the 2018 6-Series though. Would love it if Hisense updated the H9F to fix that, would probably make it my next TV.