I'm not mechanically-inclined, but I follow instructions pretty well, so I've been monitoring this thread for about six months now until I absorbed and understood everyone's advice and the tutorial posted by
crackers8199 here.
I bought a 2020 Model X SiriusXM tuner from ebay a couple of weeks ago and got SiriusXM working in my 2022 Model 3 LR with one glitch and one screwup.
I did the tuner swap without any issues but when I installed the Model X tuner there was no power to it even after several scroll-wheel reboots. So, I removed the new tuner and put in the old one (Model 3) and it was not receiving any power either, again after multiple reboots. Not knowing what else to do, I put the new (Model X) radio in again and, voila, it powered up immediately. Not sure what the glitch was but it somehow resolved itself.
The screwup occurred when, being the clumsy oaf I am, I tore the ribbon cable trying to remove it from the Model 3 tuner. Fortunately, the other FM adapter alone seems to provide the same reception as before so my clumsiness didn't result in any degraded FM performance (as far as I can tell).
I have the SiriusXM antenna mounted on the rear speaker (passenger side) as I have no idea how to mount it on the outside and put the cord inside the panel (see post 740).
Much respect to everyone here who trailblazed this path and displayed an exemplary resolve to get this working in the Model 3 (and Y).