I will first stipulate that I may not understand all of this, but this is what I need this afternoon. I am using a MacMini, 2018, with Monterey. Have an application that need to find out if it will operate with Ventura before I upgraded.
I went to the Apple Store, downloaded Ventura and when it got to the where to install I chose my external LaCie HD and proceeded. The instructions said there could be 2 or more restarts. It installed and told me to re-start to complete the installation. It booted into Ventura on my LaCie External HD on the restart. I moved my questioned app over, tried it out, it worked. I went to the StartUP preference and changed my startup back to my internal HD and restarted, it booted normally into Monterey. I have not tried to boot into my LaCie again.
