Looks like the solution (as listed at
https://cutecoder.org/programming/shared-framework-hardened-runtime/) is either:
1. sign the Pd app and disable plugin validation; or
2. use externals built for a min version of macOS 10.9
I've tried option 1 by "ad-goc" signing Millers Pd 0.50-2 build with the library validation entitlement disabled:
Please test.
We might need to add an entitlements file which specifies which things are "allowed," one of which is loading non-signed external libs. I ran into this with a project at work which uses libpd and loads a couple externals.
I just discovered the huge headache of the notarization system under Catalina: the OS will prevent loading of every non-notarized *external* that you try to load. ...