Everyone else has described the complications that a Mac mini would have. So why not consider something else? Lenovo, HP, and Dell make 1l ultra small form factor PCs and they’re pretty cheap on eBay. They’re also low power. Search for Tiny Mini Micro to find information.
I have three Lenovo Thinkcentre machines - two with 32gb RAM and one with 64gb RAM - running my Proxmox VE cluster. Highly recommend using those small machines instead of a Mac mini.
GameCube and PS2 games work incredibly well on the Steam Deck. Some PS3 and Xbox 360 as well. I’ve played through several PS2 games and all of TLoZ Windwaker on my deck.