Pixel makes it easy. They aren't benefitting from you using it if you run a de-googled OS.
If you don't want to use a Pixel, pick your ROM, then choose from their list of supported phones.
And if you think we haven't considered hardware-based back doors, you may wanna revisit 1998 when we were all talking about this as a concern - that's when I first read about Android, before it was called Android.
Edit: Prior to the Pixel, I was running Lineage or DivestOS on an Essential Ph1 from 2018. I still have one that runs well on DivestOS. Not saying to get one, just an example of what's out there.
Also lookup the phones listed as compatible with a ROM on phonearena.com and gsmarena.com