Multiple operating systems on a 2019 27" iMac
I have a 2019 27" iMac 19.1 with 2TB fusion drive running Mojave 10.14.6
What is the best method and setup to install a second selectable operating system Ie. any OS above 10.14.
I have bootable install OS's on USB go all from 10.13 to 10.17.
[Re-Titled by Moderator]