
Gil Dekel of Google has been posting patches this week to get HDR over DP MST working for the Intel driver. Today is already a second revision of the work to fix some issues with the original patch posting.
With the patches adding just around 60 lines of new code, it's then possible to enable HDR over DP MST connections. It's too late for this work to come about for Linux v7.2 but hopefully it will be ready for the 7.3 cycle.