I agree with those reasons, not sure my will is weakening, so I'll add: vendor versions of Android, the dreaded "Android" slowdown, and slower/choppier performance - generally - when comparing latest releases of hardware & software.

> and security updates at the mercy of terrible carriers.

Buy the hardware, install lineageos, insert SIM?

Is LineageOS the most trustworthy aftermarket smartphone OS out there? What makes it so?

Aren't I still bound by a GMail account for login and contact information, so if Google randomly decides to ban my account (see what happened to the viewers of a Markiplier stream), I'm in trouble?

How so? Lineage works without gapps, although obviously you then lose access to those services, including the Play Store.

I’ve never used LineageOS, I was asking. I didn’t see how you could completely separate Android and Google, especially for things like contact syncing.

Ah, okay. So the simplest case is that you just don't have those features through Google so you have to find another provider. For instance you can do contact sync through CardDAV courtesy of apps like https://www.davx5.com/, email with K-9 Mail, get apps from F-Droid, etc. Depending on exactly what the problem with Google is, you can also use unofficial software that still talks to Google services like https://microg.org/ instead of play services and newpipe instead of the official youtube app.

LineageOS comes with AOSP stock applications and you can install additional app stores on it. You can also install the google apps packages including play store and play services, but you don't have to. Of course many 3rd party apps rely on play services e.g. for payment.

It’s great, but you need a phone that’s popular with its developers.

I totally agree. Apple is great for privacy - and that's important to me - but I'm slowly starting to think I might move to something else. Sadly, it seems my only real option is Android. I miss windows phone and blackberry.