Migrate OS to new SSD without upgrade?

I bought a new SSD for my Macbook Pro early 2015 and tried to migrate to it yesterday. I'm still on Big Sur, and of course internet recovery forced me to upgrade to Monteray at the same time. It worked, but I discovered that it could no longer access my NAS over SMB. Presumably Monteray has broken this in some way and I have to wait for either Apple or AVM to come up with a fix. In the meantime I'm back to the original SSD.

Is there any way for me to migrate my OS to the new SSD without upgrading to Monteray at the same time?

Solution 1:

of course internet recovery forced me to upgrade to Monteray

You don't have to install the latest OS. Which one you're offered depends on what startup key combo you use:

On an Intel-based Mac, if you use Shift-Option-Command-R during startup, you're offered the macOS that came with your Mac, or the closest version still available. If you use Option-Command-R during startup, in most cases you're offered the latest macOS that is compatible with your Mac. Otherwise you're offered the macOS that came with your Mac, or the closest version still available.

It sounds like you used ⌘⌥R, but should use ⇧⌘⌥R instead.

https://support.apple.com/en-us/HT204904