Fairphone is an option. Can be relocked. It is not important, what Fairphone supports but if it is supported by custom ROM developers. Fairphone is supported by most. But please avoid using Calyx or iode. They are both outclassed by Divest.

At least for /e/OS I can assure that relocking is simple enough. As there is partnership between Fairphone and Murena (/e/ developers) OTA updates are safe for future. Unfortunately the Fairphone support is horrible and /e/ is always too far behind security patch level.

Graphene only supports Pixel

It is not. Please educate yourself a bit more. They obviously cannot randomize all data. It is more a besteht effort approach.