You could use it for Windows 98/XP retro gaming if you add a graphics gard, but for anything else it’s far too inefficient to be useful

Not quite - even in PowerShell 7 there are some features that only work on Windows and Windows only comes with PowerShell 5.1 by default.

I can’t see the picture, but if the Mac Mini is from late 2018 or newer, the iGPU should be able to transcode 4k video.