> But once I saw how smartphones were being designed as surveillance devices, I refused to play.

Get a FOSS Android phone. I have a OnePlus 7 Pro, previously a Galaxy S5 (the newer Galaxys also work as long as you don't get the US model); it runs LineageOS (stock Android). I chose not to install the Google Play packages. I get apps from F-Droid, which is a repository + package manager that builds and distributes FOSS applications.

It pings time.android.com for NTP, and I think it also uses a Google server to check when you're behind a captive portal WiFi. The default dialer/SMS/Contacts app have some options in the settings that will connect to proprietary APIs; I don't think they talk to Google but if you do then you can replace them with applications from F-Droid. But other than that it's 100% clean.

In the system settings I can completely block applications from using the network. LineageOS also adds Privacy Guard, which lets you deny permissions to applications. I need WhatsApp to communicate with some people, but I have denied it contact permissions so it gets fed an empty address book. I also have it set to require confirmation from me to use the camera or microphone.

I also installed AdAway from F-Droid, which is a DNS-based firewall like Pi-Hole. From F-Droid I also got Firefox with uBlock Origin, K-9 mail client, NewPipe as a YouTube frontent, OsmAnd+ for maps/navigation, DavDroid to sync contacts & calendar with Nextcloud, the Nextcloud Notes app for synced notes, and a OpenVPN client to prevent AT&T from spying on me and injecting tracking identifiers into my internet usage.

The only real threats in the system are the proprietary driver blobs and the risk of Google putting evil code into AOSP instead of limiting it to their proprietary services - but I hope the LineageOS team would be able to catch that.