Both ports will display video on boot, but neither will give audio on boot. Regardless of which port is used (HDMI or DP) on boot, if I swap to the other one after macOS is loaded, then audio will work on the newly switched to port (yes, both DP and HDMI). Audio works on both my HDMI and DP...
Sorry, I've added my profile details.
To clarify, my Zotac card has two HDMI outputs (one is native HDMI, and the other is DisplayPort with an HDMI adapter). I need to swap the HDMI ports used every single time I start up to get HDMI audio working again.
I have the following card:
ZOTAC GeForce GTX 1050 Mini 2GB (using up-to-date nVidia web drivers)
I've followed the stickied guide in HDMI Audio here (Audio - HDMI Audio AppleHDA [Guide]) and Toleda's script