I sent this to Corsair support. Ya'll will get the picture by reading this with that it mind.

"Hello Corsair Support,

I previously wrote to you asking if my Corsair Virtuoso XT headset could communicate through the microphone via bluetooth in order to run on my Steam Deck. The ultimate answer we arrived at was no.

I had previously mentioned that I would experiment with the included USB fob.

This experiment has come to fruition, and I would like to fully confirm that the USB fob works on Steam Deck and enables the microphone without a problem. Furthermore, the USB fob is plugged into a Sabrent 10-in-1 USB adapter purchased from Amazon.

Hopefully if someone else has this problem, this is a solution you can point them to. However, it only works when docked as the Steam Deck only natively has a USB-C connector.

Final bit of data just to cover all corners, my deck dock is a JSAUX, also from Amazon, 5-in-1.

It is my hope that this settles this question for all who come after me."

(Also posted this on r/SteamDeck to proliferate the info)