AudioBus 3 is available at the Appstore and now has support for Audio Units.
The app is $9.99 and I consider that a high price for app of this kind. The AudioBus is just providing interface that other app developers can implement so the AudioBus to be able to connect their app with each other. The old version was not supporting swift (as the new one) so the new apps were just out of the list. Now the support for Apple’s Audio Units will partly fix that making connection with modern swift Audio Units.
If you have the old AudioUnit 2 you will still need to pay for the new version which is very high price!
The app has nice UI to make the all the connections but still miss some needed features for fine controlling the Audio Units.
Here is a video: