Installing Monterey on Mac Mini external SSD
I have a 2014 Mac mini that has an internal HDD formatted MacOS Extended (Journaled) running High Sierra 10.13.6. I want to upgrade it by installing Monterey on an external SSD, then swapping out the internal HDD for the new SSD. I have a bootable Monterey installer flash drive. I have already formatted the SSD as APFS. And I understand how to open the mini and swap out the drive.
Must I first install Monterey on the existing internal HDD before installing Monterey on the external SSD? I recall hearing something about this in the past. This would, of course, require reformatting the internal HDD as APFS. I prefer not to reformat & install Monterey on the internal drive because I want to preserve the 32-bit apps that are on the HDD.
Or can I just boot from the bootable Monterey installer and directly install Monterey on the external SSD without involving the internal HDD at all?
(Note, pls. ignore the profile listed below, which indicates a 2018 mini. This is about my 2014 Mac mini.)
Mac mini (2018)