If you buy a new Pixel and then run an alt rom like graphene or lineage, you’re most likeley costing Google money. I believe they manufacture the Pixel at a small loss because they expect to make their money back harvesting and selling your personal data. Denying them that should mean you get decent hardware at a fair price, without really “supporting” Google as much as you fear. I could be wrong, but I’ve definitely seen that mentioned before.
+1 for pihole! Stupid easy for linux geeks to setup and maintain, but probably a pretty hard sell for the more general public. A cloud service like NextDNS might be more appropriate for average Joes. I can’t speak to AdGuard since I don’t use it, but I know that name gets mentioned frequently in privacy circles - favorably, I think…
I have a Brother color laser printer (technically it’s like LED or something? not home, don’t have the exact model handy). It has built in wifi and ethernet for network printing. The wifi isn’t configured, and the ethernet is manually configured with a static IP for my LAN… but no gateway address. This breaks outgoing network connections to the internet (as evidenced by the printer’s inability to check for firmware updates), while behaving otherwise normally for all my LAN devices. I hope this info is useful!