If you want a phone you can trust, you might like a GNU/Linux phone (Librem 5 or Pinephone).

(I know this doesn't really help you now, but) If you install your self-representing operating system as part of setting up a new phone, then you don't end up in a situation where it's some huge disruptive undertaking. Also doing so within the purchase return period assures that your phone can definitely be unlocked, rather than finding out otherwise when it's too late.

Since the main reason not to use grapheneOS is that it only supports Pixels and you already have one, you might also consider it. Install feels almost suspiciously easy coming from the likes of cyanogenmod.

https://grapheneos.org/