Question about upgrading 2014 Mac mini w/High Sierra to Monterey
I have a Late 2014 Mac mini currently running High Sierra 10.13.6. All is well.
I'd like to upgrade it to Monterey by installing Monterey on an external drive. And keep the existing High Sierra installation on the internal drive. This would be a dual-boot configuration.
The internal drive is formatted MacOS Extended Journaled for High Sierra. I know that the external drive will need to be formatted APFS, in advance, for Monterey and I believe I would have to do that via Disk Utility in my current High Sierra environment before installing Monterey on the external drive.
I am aware that macOS installers (including Monterey) usually include a firmware update.
If I go ahead and download/install Monterey on an external drive attached to the mini, will the firmware update in any way preclude or interfere with continued operation of High Sierra if/when I attempt to boot again from the internal drive?