Mac Mini late 2012 resolution issue

[kizkoip]

Hi! So here is the thing: I've got a 2012 mac mini and I do know that it does only support 1080p via the HDMI cable. That being said I bought an active MiniDP - HDMI adapter which converts thunderbolt signal into HDMI and exerts up to 4k resolution.

I also have a 2K budget monitor from Xiaomi which only contains an HDMI imput. And this is the case:

- When I boot my Mac mini and see the drive selection window - it exerts 2K resolution
- When I boot in Windows 10 via BootCamp on the very same Mac - it exerts 2k resolution

But as soon as I boot normally into Mac OS and encounter the password window (tried Big Sur and Catalina) - it switches back to 1080p and stays at it.
I even tried my 2013 11' MacBook Air with this adapter and it does exert 2k in Mac OS Big Sur, but my Mac mini for some reason would not - only while I load up the system.

I tried deleting the display properties in Library/Preferences, but nothing changed. Maybe there is some advice I could ask for?

 

[for this]

Since the setup (the active adapter and the HDMI cable) appears to work with your MacBook Air. So the adapter and the cable should be OK.

There are many threads about resolution problem when using an active DisplayPort to HDMI adapter with the Mac Mini 2012. I've found only two threads so far that have the OPs report successes. Many others threads are just abandoned halfway.

Active MiniDP to HDMI adapter not working - Apple Community

discussions.apple.com

Possible to get 1440p from a 2012 Mac Mini via mini DP -> HDMI adapter?

I recently purchased a 2012 Mac Mini and am attempting to max out my dual monitor setup. Currently, I connect my Mac to a Dell S2417DG's HDMI 1.4 in via this passive mini DP to HDMI 1.4 cable. Acc...

apple.stackexchange.com

The OPs in both of these threads have tried SwitchResX at one point before switching to a "true" active adapter. It's not clear whether they still need to use it to achieve the resolution but it may be your ticket.