Wolf contact Apogee about this, they are very helpful!
Tomorrow I’ll wil try Overbridge on a 27" iMac (OS X Yosemite) from 2011 with the Apogee Symphony I/O in USB mode.
Yes, at least with the Duet 2 you can still get a lot functional use just from the hardware big button, and assignable touch screen buttons. I don’t really need the Maestro software as I don’t often change any of the settings that can only be changed from Maestro.