I have yet to find a satsifactory way to disable them - it's pretty easy to disable notifications from userspace apps like Instagram or Snapchat or whatever, but disabling notifications or altogether uninstalling vendor apps is a huge pain in the ass.

Most advice I've gotten has been flash a custom Android kernel or a de-Googled distro. This would definitely solve my problems, but this removes the ability to install Play Store apps which are a necessity for me. Not to mention that it gives the possibility of bricking my phone, which is way outside my risk tolerance for just getting rid of some annoying ads.