The updates after 19C did contain fixes for Sirius XM not working for some. The updates may fix it.
All you have to do, is start the update with the car on. It does not matter if the doors are locked at that point. Once the update downloads, there is a period of time where it is doing prep work for the update. It will put out a message in that update screen saying it will install the updates after the car is shut off. That is when you shut off, get out, lock it and walk away for at least 15 minutes. The next time you get in, everything will seem normal when you power it up, but after a few minutes there be a little message saying the update has installed.
If it installs S20A, then it will probably prompt to install the next update after that S20B and after you install that repeat the process with S20B1. Eventually, we hope, you'll get up-to-date on the infotainment software.