These cars are sold with data plans which last quite a few years. What model year is your Blazer? I think that my Equinox has app access for 3 years and maps / google assistant for 8 years. I've tested tethering with my phone and it works with that, so I have a path forward once the built-in subscription lapses.

This is the one that I saw: https://evplay.io/shop/ev-play-lite-gm

It's kind of expensive, and there's a non-zero chance that GM does something to block it.