On the newest model Mini, the hard drive is soldered to the logic board. It's *NOT* user upgradable (unless you've got a massive set of balls).
Apple’s goal is to make it impossible for the user to do any upgrades, of course this means their “ genius’s” can’t do anything either.
So... Much like going back to Apple's golden years?
I had a mac laptop that needed 3 motherboards in a 3 year span.. Same issue every time.. Was told every time that it was my fault and I would have to pay for it despite the forums full of people complaining about the same problem happening to just about every Mac at the time.. Apple never admitted a production issue and soon after switched to Intel.
The fourth time it happened I learned how to do BGA reflow with a hot air gun and fixed it and sold it.
If you buy a new MINI, it HAS to run 10.14 that it comes with-it won't have drivers for the machine in older OS versions....Apple doesn't put bloatware on, so....why are we discussing cloning drives again?
....there's no internal SATA connection for a second SSD to be added. Buy what you need for OS, apps for it's lifespan from Apple. Budget for a Thunderbolt external chassis with SATA connectors to handle your old SSDs and all the project and sample storage.
This is a question I asked in the release thread and never got an answer to....which is why I post it here. No secondary SATA SSD possible in the 2018 minis. You CAN upgrade the RAM....FWIW.