For Subarus, I found this.
https://www.geraldjustprojects.com/product/dcm-delete-module-gen2/
I had to use this on my car because the speakers are routed through the DCM module. Not every vehicle requires a delete kit or replacement module, but some do. As with any aftermarket car modifications, check the year, make, and model for compatibility.
In general, looking for “Onstar/DCM delete” tends to work.
There are delete/bypass boxes available on the aftermarket, and some models can be directly unplugged with no side effects (other than Emergency Response or Onstar not working).
It tends to be more “I want a thing that just works.” rather than no technology, but yes.
Self-hosting services that are reliable and don’t get in my way, not using cloud-connected smart devices, running Linux instead of Windows, etc.
Yep. Explained in another reply above, but I had to do the same thing on my Subaru-manufactured car.