Is this a Marvel Snap reference?!

I can’t speak for Canada but at least here in the US, I’ve used every Pixel on any carrier I wanted. And most of them were small ones. Straight Talk, Ting, T-Mobile, and one more I can’t even remember the name of.

IIRC, the “allowlist” stuff was just “known carriers that use towers that are compatible with this phone.” As in, different carriers use different “bands”, or frequency ranges, for their transmissions. Your phone has to have hardware support for those bands. So the “allowlist” is really just “we know these work.” I’m pretty sure neither Samsung nor Google will stop you from using an unlocked phone bought from them with any carrier that’ll accept it. These days, I just stick a SIM (or eSIM) into my phone and just go.

What’s probably happening here is your adapter is signaling some button press when you connect it that’s popping up the Assistant. Only way to fix that is to get a new adapter since you can’t manually disable that input from triggering the Assistant without root.

However, you can completely disable the Google Assistant from appearing at all via:

Settings > Apps > Default Apps > Digital Assistant App > Default Digital Assistant App > None

That should fully disable it in all regards and it’ll never pop up again.