Joe is buying a new Mac Mini and wants to know if he can install macOS BigSur onto an external hard drive and run from that. Leo says you can, sure. But make sure you format it to APFS. But what about Pro Tools. Leo says that Pro Tools doesn't support Big Sur yet. That's not a good sign since major studios are using it to record music. And he's heard that Apple may continue to sell an Intel version of the Mac for that very reason. So since Joe uses ProTools, he may want to stick with macOS High Sierra since he needs ProTools to work consistently.
What about using a third party cloner? Leo says that for BigSur, Apple requires a signed and approved version of any app for security purposes, and no third party cloner will do that yet. Leo suggests reading this blogpost from Mike Bombich about making a bootable backup.