Converting Displayport 4K to HDMI 4K 30Hz.

Sandberg Adapter DisplayPort1.2>HDMI 4K (508-95)

This one HDMI 4K 60hz
https://www.uptab.com/displayport-1-4-to-hdmi-2-1-8k-60hz-or-4k-120hz-hdr-active-adapter/

As of 2019, I'd say a good 4k TV is good enough for trading. Its also nice to have the flexibility in your items for future use.
Colour isn't quite as vivid as say a top monitor. But then its as good as a fair quality monitor.

I had a Toshiba but I had to reduce my resolution by about 250 pixels from 3840.
The Toshiba was sent back once then it failed after a year (5 yr warranty fortunately).
Swppaed for a slightly more expensive Samsung. Samsung is better quality and no resolution adjustment needed, quicker on boot up too.

I'd recommend a good TV. But Toshiba (now a Turkish company with licensing from Japan) are not as good as Samsung.