How to reproduce:
# Open the project “IN-64237_HDRP_Multi-Camera_UI_HDR_Tests“
# Open “Test B“ scene
# Drag the Game window to a -4K 10-bit- HDR-capable display and maximize it.
# Enter Play mode
# Observe Game window UI text "HDR is OFF" and press "H" key to enable it
# Observe the Game window

Expected result: Game window is displayed properly with the UI
Actual result: Game window turns black

Reproducible with: -2021.3.34f1,- 2022.1.0a16, 2022.3.17f1, 2023.2.6f1, 2023.3.0b2
Not Reproducible with 2022.1.0a15

Reproducible on: Windows 11 Pro (23H2), Mac M1 Mini, Macbook Pro 2018

Note: a workaround is to Enable the “S Camera” and disable the “Black BG” (child of “Canvas”).
Note: Does not actually require 10-bit 4k monitor, just an HDR capable monitor.