Watching HDR10+ content on displays that don't support it?

I'm thinking about buying a new TV but I'm struggling to find some decent technical info on HDR10, HDR10+, and DolbyVision. One of the TVs I'm thinking about buying doesn't support HDR10+. If I tried to watch HDR10+ content on it, what would happen? Would HDR10+ content from a blu-ray, for example, just not play because the player wouldn't be able to "negotiate" HDR10+ with the TV? Or would the player convert it to HDR10 that looked more or less as intended? If I got an HDR10+ file (assuming such a thing exists; I assume someone's come up with a way to put HDR10+ metadata in an MKV) and played it directly on the TV, would it be likely to just ignore the HDR10+ metadata, and would it therefore show scenes with the wrong brightness and contrast?

It is possible to approximate HDR10+ using Dolby Vision 3 segment curve. So, just need someone to come up with it.

Blu-ray does not support profile 5.

From what I was reading this is incorrect, and there have been some discs authored with Profile 5. I forget which, but there's been discussion on it somewhere here :)