Pixel 7 / pro (8 I think is too pricey, but that phone is my personal benchmark)
8th generation Pixels provide a minimum guarantee of 7 years of support from launch instead of the previous 5 year minimum guarantee. 8th generation Pixels also bring support for the incredibly powerful hardware memory tagging security feature as part of moving to new ARMv9 CPU cores. GrapheneOS uses hardware memory tagging by default to protect the base OS and known compatible user installed apps against exploitation, with the option to use it for all apps and opt-out on a case-by-case basis for the few incompatible with it.