But you can connect with the app to the care via Bluetooth. I bought a small Bluetooth speaker too, just in case. Phone charges may apply. Depends on the carrier. It even worked in Hawaii, where there is no SiriusXM service.

The app will play in the car

It will be far easier to manage.
To use Sirius from the radio would require you to transfer to the radio ID in the rental and then back again after.

the rental car computer can store your data. Contacts, etc. This is one of the many reasons I don't like smart phones. I use an old fogey flip phone with buttons that only makes phone calls.
About a year ago, WaPo published an article about phones and rentals. They were assisted by a white hat hacker. They rented a car and extracted data for SEVENTY past renters. I didn't find that article right away, but I found this below. Sounds like the same project.
https://protectme.blog/devices/connecting-your-phone-to-a-rental-car/

"After hacking into an infotainment system they discovered:

unique identifiers for previously connected phones;
detailed log of phone calls;
text messages;
photos; and
and entire contact lists including other people’s names, address, and emails."

A black hat hacker could rent a car for a day and get a trove of data.

This is a related article on WaPo:
]https://www.washingtonpost.com/technology/2019/12/17/what-does-your-car-know-about-you-we-hacked-chevy-find-out/
"Among the trove of data points were unique identifiers for my and Doug’s phones, and a detailed log of phone calls from the previous week. There was a long list of contacts, right down to people’s address, emails and even photos."

Be wary about pairing a phone with a rental car. Once you return it, it still holds your data. I bet there's something in the rental contract fine print about this. Maybe not.
This isn't even a free service, but:
"If the service is free, YOU are the product."
We are all data mines for the monetizers.

Play the radio. Use the phone when you're not driving.

I'm taking my good old iPod too. I'll be driving long distances so that may just be good enough.

Thanks!

I use an ipod touch for camera and music. No phone circuitry, no internet, no communications -- it doesn't distill my whole life in my pocket. With good earbuds or headphones, it's a decent sound system.

Make some playlists, you can start it and let it run in your pocket.

Using the Sirius app requires (1) a cell connection, so coverage isn't as universal as getting it from the satellite, and (2) internet access over your phone.

Depending on your wireless phone contract, you might want to be careful about burning up the megabytes listening to Sirius.