Sorry it took a while for me to reply, I didn't notice this.
Unity 2022.3 and up supports it. It was back ported to 2022.3 from 2023.1. I've noticed myself official documentation doesn't mention this but it is supported.
Tho only 2023.1 has mobile support for HDR.
Also to dev properly in HDR you must also be using an HDR display. I've known devs to struggle with HDR support when developing on non-hdr displays for post process effects.