Best powered USB hub for my 6 or 7 USB 3.0 HDD media library drives with either an M2 Mac mini or a new M4 mini?

Plugable, Tplink, and Anker all make 7 port powered USB 3.0 hubs. The port layout and spacing is a bit different but one of those three should do the job. I would avoid the random amazon junk brands with nonsense names.

Ditch the USB and look into Unraid.

Plug those drives (any size) together into a cheap used PC and use Unraid to join them up into a monolithic array that can also use recover from drives failing with zero data loss and effortlessly scale larger by adding new drives of any size, mixing and matching as you like.

It’s the single best computing investment I’ve made in the last two decades and can scale as big or small as you like.

Yes theres a free demo version.

Would you consider purchasing an enclosure like what Yottamaster offer? I do this with a Raspberry Pi 4 and it’s perfect.

Otherwise I’m confused. Are you looking for a hub to power that many individual hard drives?

I'm not sure about specific models, but you should strongly consider a Thunderbolt connection and enclosure for your drives if you're already shelling out for a Mac Mini. Way higher throughput and no need for external power!