From the Dorico 4 Version History PDF:
Universal app on macOS
Dorico 4 is now a Universal app, which means that it runs natively on both Intel- powered Macs, and on the latest Apple silicon Macs, such as the M1 MacBook Pro, iMac and Mac mini. If you have an Apple silicon Mac, Dorico will run as a native application by default.
VST plug-ins. When running natively on Apple silicon, Dorico can only load VST plug-ins that can run natively as well: it is not possible for Dorico running natively to load VST plug-ins running under Rosetta 2, the technology that allows software built for Intel-powered Macs to run on Apple silicon Macs.
In addition, there is no support for VST 2 plug-ins on Apple silicon, so when running natively on Apple silicon, only native VST 3 plug-ins will appear.
If you still rely on one or more VST 2 plug-ins, or if a VST 3 plug-in you rely on is not yet available in Universal format, you can force Dorico to run under Rosetta, which will allow VST 2 and Intel-native plug-ins to be loaded, though at the expense of slower overall performance.
To force Dorico to run under Rosetta:
- Quit the application if it is running.
- Locate Dorico 4 in your Applications folder.
- Select the icon and type Command-I to open the info panel.
- Activate the Open using Rosetta checkbox.
When you next start Dorico, it will run under Rosetta.