It was apparently built for a very specific use case (doing CI for some application) so I guess it has to be ARM Linux. You can run Linux in a VM guest on Mac mini, but some limitations remain:

- The project was obviously started before the Mac mini was available

- Linux guests are still rather experimental and might not behave the same way as a real machine.

- 32-bit Arm applications do not run on the M1, it is a 64-bit-only CPU

- Nested virtualization is said to not work yet under MacOS, so you cannot run KVM guests inside of the Linux guest

- If you need to spin up lots OS instances simultaneously to test various setups and each of them need 8GB, you can have at most 2 instances on a Mac.

For most use cases, none of those apply, so you would be better off with a Mac, a Graviton instance or an off-the-shelf PC.

Maybe. But you have a network bottle neck between the 14 separate computers that you have on a single computer. If you have a computational task you split in 56 pieces and run it across the setup, you can utilies the cores fully. However even in that case I think the Mac Mini will outperform this.

You can use it as a USB-hub though as I suppose you get 2 USB-ports pr. raspberry pi.

Here's one off the top of my head:

Serving web pages. A single Raspberry Pi 4 can manage 943 Mbit on its Gigabit port.

You might be able to buy (expensive) 40 Gigabit network adapters for the two TB4 ports of the Mac Mini. You'd still be slower.

Maybe some ram based application? Opening 100gb csv in pandas? Redis with more than 8gb data?

I doubt it - each cpu core only has access to the 4 or 8 GB that is on its machine - to communicate to other parts of the setup it will have to go over network or a shared drive. I think that will be much slower than a highly integrated device like the mac mini just using its hard drive.

Controlling several hundred WS2812B LED strips, perhaps?

Or a kiosk with 14 HDMI displays.

Sure. But wouldn't you then put the computer inside the display?

Something IO-bottlenecked maybe?