PaulEF

I'm interested in adding Apple Carplay to my 2015 Allroad if that's even possible. I've seen the Carlinkit Wireless Auto Smart Box, which appears to require only
that I have MMI and an aux option.

I do have MMI (no more 3g however), but no aux. Instead I have an iPod adapter cable in the glovebox. I gather I could use another adaptor such as to get the aux input.

Has anyone setup Carplay in such a manner? Am I overlooking some other approach? Are there general suggestions for what I'm trying to accomplish?

SMac770

The connected functions of MMI 3G+ are not relevant to the Carplay solutions out there. That page says AMI (Audi Music Interface, the port in the glovebox) or AUX, which is the normal expectation.
The CarlinKit is an example of the hideaway interface box solution. It reuses the existing low res non-touch OE screen.

Then there's the replacement screen device solution, which is basically an Android touchscreen tablet in place of the old screen.
https://rsnav.com/collections/s3-android-9-0-system

There's more than a few threads in the B8 forums on both solutions.