Chosen Solution

Did anyone know the power output on the 3.5mm jack on 2020 and later Mac Mini’s?

It’s a standard 3.5-mm headphone jack. The new Mac Studio offers 3.5 mm headphone jack with advanced support for high-impedance headphones! If that is what you want to know. Headphones are measured by their Impedance not Voltage, here’s a bit more: Headphone Buying Guide: What Is Headphone Impedance?