My apologies if this has been mentioned before, but, after much research, I have found three ways to get your Tesla to scroll through SiriusXM favorites using the steering wheel buttons. These only make the scrolling through favorites work for the duration of a drive, so you'll, unfortunately, need to do them each time you get in the vehicle.
1. Change from your driver profile to a different driver profile. Change back to your driver profile.
2. Manually delete all your SiriusXM favorites. Set them back up again.
3. Reset vehicle's entertainment system. This deletes all your SiriusXM favorites. Set them back up again.
I use option #1 each time I get in my vehicle. I have a duplicate profile for myself so this just requires 2 presses on the screen each time I get in the vehicle. It's a bit of a whip, but it's better than nothing at this point.
The good news here is that, with all these three options (especially the 3rd option, which resets the car back the first time you drove it when you received it from the factory) addressing the issue, this proves, in my mind, beyond a shadow of a doubt, that, despite all the Tesla representatives' assurances to us that "This is how the SirisusXM radio on your Tesla works and it is not a software glitch", this MOST CERTAINLY is a software glitch. And Tesla needs to stop gaslighting us on this, admit that they are wrong and fix this issue.