the one you get for free off the back of a truck /hj

in all honesty the t480/580 probably. modern enough to have decent power, latest one with libreboot, and old enough to have some level of modding scene. t580 is a bit less known but mostly the same just larger.

honorable mention goes to the a485 as it's the ryzen twin of the t480. doesn't have libreboot and slightly worse CPU performance for an infinitely better iGPU without dealing with nvidia and the higher power consumption/worse drivers.