This info is available on
the Mac mini Tech Specs page at Apple:
Simultaneously supports up to three displays:
- Up to three displays: two displays with up to 6K resolution at 60Hz over Thunderbolt and one display with up to 4K resolution at 60Hz over HDMI
- Up to two displays: one display with up to 6K resolution at 60Hz over Thunderbolt and one display with up to 4K resolution at 144Hz over HDMI
- One display with up to 8K resolution at 60Hz or 4K resolution at 240Hz over HDMI
Thunderbolt 4 digital video output
- Support for native DisplayPort output over USB‑C
HDMI display video output
- Support for one display with up to 8K resolution at 60Hz or 4K resolution at 240Hz
Video Playback
- Supported formats include HEVC, H.264 and ProRes
- HDR with Dolby Vision, HDR10 and HLG
Given it says it can playback HDR, I'd guess it supports it in a display output.