3 Months of Spotify Premium With Xbox Game Pass Ultimate Membership.
Open only to users who haven't already tried Spotify Premium
You can claim it in the Perks section on console, from the Xbox Game Pass mobile app, or the Xbox app for Windows 10 PC (but not from the web).
On my Xbox One X the Perks section can be accessed from the home screen, by clicking on "Claim your perks now".
You're probably right, I searched Ozbargain to see if it has been posted before, but I couldn't find an active one.
There were a lot of these deals with Spotify and other incentives, since Microsoft introduced the Ultimate membership.
But the deals posted on Ozbargain before have now either been marked as expired, or they differed slightly (eg different number of months of Spotify Premium was offered, but mostly they have expired).
TBH the large number of these deals makes it look a bit like a long running deal, with small changes in between, so it wouldn't surprise me if the same deal (or a very similar one) had been posted before.
Redeemed this offer yesterday then upgraded to Premium Duo plan & got just over 2 months free (My Premium Duo plan renews 21/10/20).
I could've sworn this was posted before but I have only been able to find a few comments and no actual deal post.
Either way, good awareness :)