I have a 2019 3500 gas SRW with a Northstar cabover camper. My Sirius works about 70% of the time and is dependent on the direction of travel for it to work.
On my past truck (2013 GMC) I was able to buy an antenna from Sirius and an adapter (FAKRA) to plug it into the GMC antenna port. This port was located behind the glove box and was easily accessed.
On your new truck the access port for the antenna lead is in the dash behind the radio screen. I am unsure if a FAKRA connector will work with this and I have been afraid to pull the dash apart to check.
Please post if you come up with a solution
Bill