DisplayPort to HDMI adapters need to be active instead of passive to work properly and reliably at 4K. Active adapters tend to start at about $15 as of this posting.
https://blog.tripplite.com/whats-the-difference-between-passive-and-active-displayport-adapters
Thanks.
Been looking for a couple of DP+ cables, and had forgotten this info.
It’s been rough ever since Tanner Electronics closed in Carrollton.