We've found that the ASIO2 (16 or 24 bit) drivers for the UA20 work in DP3. You may find that DP's Configure Hardware Driver window alerts you that there is no compatible device attached, but if you continue choosing the UA20 ASIO2 driver, it will work.

* Make sure that the UA20's ADVANCE mode switch is ON when using ASIO drivers.

This has been found to work with the UA700