I tried using the System Information app.
- No item listed for “DisplayPort”.
- The “Graphics/Displays” item lists video cards.
- The “Thunderbolt” item has no information about DisplayPort.
Apple does not document this important information. For example, this Apple Support page, Mac mini (2018) - Technical Specifications says only:
Thunderbolt 3 digital video output supports Native DisplayPort output over USB-C
Four Thunderbolt 3 (USB-C) ports with support for: DisplayPort
…with no mention of which version of DisplayPort standard.
This Question seemed to be asking this question. But it is not exactly clear. And no Answer directly addressed the issue.