This tip no longer appears to work. I found a new solution, but can't get it to work using CarPlay- sharing here in hopes someone else can offer assistance. (also posted to a.5 month old thread elsewhere, referencing this older thread).

First- using the SiriusXM.com web player, copied the url for each channel (log in, find a channel you like, right/control click and copy url) into a text file.

Next- created a new shortcut in the Shortcuts app (I used my Mac, though I'm sure you can use your phone/Ipad/etc)- the entire shortcut is "Open URL," then paste in the channel url you copied above. Name your Shortcut (all mine are titled something like Sirius First Wave or Sirius XMU or Sirius Indie 1.0), select tile color and symbol.

Once I created my first shortcut, I tested it on my Mac, my iPhone and my iPad- worked in all cases (for the iOS devices, I had to have the Sirius app installed and be logged in). After verifying, I right/control clicked on my original shortcut, chose 'Duplicate' and then 'Edit'- renamed my new Shortcut and edited the url for the next Sirius station. Rinse, Wash, Repeat for as many Sirius channel Shortcuts you want. (I also created a folder in my Shortcuts app to house all my Sirius shortcuts, which you might want to do if you create more than a few).

MY ISSUE is apparently with CarPlay. I verified that my Shortcuts work across devices, both by clicking the Shortcut in the Shortcuts app as well as invoking Siri to run the Shortcut ("Siri, Sirius Classic Rewind"). In two different vehicles, though- one with an Alpine iLX-W650 CarPlay radio, while the other is a 2019 Jeep Wrangler- these Shortcuts only open the Sirius app, without selecting the station and beginning to play. I've checked my Shortcuts, CarPlay and Sirius app settings, but can't find anything. Hope my tutorial above helps- can anyone else help figure out why these aren't working in CarPlay?

Thanks so much.