Other options are Fairphone, Volla, Murena - or flashing “vanilla” custom ROM’s on phones other than Pixels - or using Ubuntu Touch, Plasma Mobile, Mobian, Droidian or Sailfish OS.

Its kinda ironic that google pixel is the only phone with decent secirity hardware and an unlockablw bootloader.

Buy a second-hand Google Pixel.

1. Buy an old Xperia 10 III.
2. Flash SailfishOS there
3. ???
4. Profit

They would make a lot more money on that purchase if it’s vanilla android though. Yes, you’re spending money on the hardware, but is Google really known for making bank on just hardware sales?

buy a used phone