[BelenusMordred]

People here are saying Oneplus, but I would recommend Pixel 4/5 or Xiaomi Mi A3 with stock Android One to fallback on if you don't like using LineageOS.

Oneplus have become quite end-user hostile lately. They used to be quite good for this stuff but times do change.

If you go the Pixel route, there's also GrapheneOS (formerly Copperhead). It offers a lot more security features, with of course some tradeoffs when you make a phone secure.

https://grapheneos.org/

[infogulch]

It seems GrapheneOS recommends Pixel 5 or Pixel 4a 5G for the longest expected support window. [1]

[1]: https://grapheneos.org/faq#recommended-devices