Raspberry Pi 3 Model 3+Schiit Modi 3+, Can't Find DAC In Set-Up?

I d/l’ed Volumio V. 2.861 (12/22/20) to a Raspberry Pi 3-Model B V1.2 initially, ran the initial system set-up. All is well until I select the “Audio Output Device”. My understanding from Schiit customer service is their Modi3+ should be shown in Volumio’s list of DAC’s to select.

My set-up choices:
“I Have An I2S DAC” — No
“Select Your Audio Output” — HDMI Out/Headphones/Hifiberry DAC

Question - should I not be able to see a selection choice for “USB” here, as well? Logic would dictate that this is the case, as I have no intention on using any of the options selected to connect to the Modi 3+.

Per Schiit tech support, their DAC should be listed by Volumio as an option. I thought maybe the Raspberry Pi Model 3 may not be supported by Volumio, so I purchased a new Raspberry Pi 4, 4 GB RAM. Same effect.

I’ve noted other users on this forum stating they have successfully set-up both The Raspberry Pi 3 and 4 with the Schiit Modi 3+ DAC quite satisfactorily. Any ideas?