No one has brought up Unraid OS specifically yet. Others have said just build your own machine, and yes absolutely this is the way. And then just slap Unraid on that and you have yourself exactly what you’re looking for. It’s user friendly, as powerful as your wallet can handle, and plenty of room for expandability.
Every year at Christmas my grandparent in law asks me to fix her iPhone. Something with iCloud account. The answer is always the same: Apple store.