Mac OS X:
- the package is now code signed and notarised in order to avoid installation problems on OSX Catalina.
But is still possible that the downloaded files will be "quarantined" by the OS, and the externals will not load in Max. To avoid that, you need to remove the quarantine executing in a terminal the following command :

xattr -d -r com.apple.quarantine [path/to/extern/directory]