“myexternal~.pd_darwin” cannot be opened because the developer cannot be verified. macOS cannot verify that this app is free from malware.
The buttons accompanying this message are Move to Trash (!) and Cancel.
There are probably other ways, but to fix this, I had to go to System Preferences > Security & Privacy and click the button that allows authorization for the last binary that was prevented from launching.
I then had to quit and restart Pd. Opening a patch containing the offending external, I’m greeted with an error message similar to the first:
macOS cannot verify the developer of “myexternal~.pd_darwin”. Are you sure you want to open it? By opening this app, you will be overriding system security which can expose your computer and personal information to malware that may harm your Mac or compromise your privacy.
You get Move to Trash, Open, and Cancel buttons this time. If you say Open, your external is allowed to load from this point on. But note that you have to do this 3-step process for every external, and only at the time that they’re first loaded, meaning we’re going to have to go through this whenever we first load up some old patch with a (64-bit) external we haven’t used in a while : \
Kevin