Any halfway serious GPU-related stuff on any mini would probably need an external GPU in 2018, until Apple unwraps an updated mini this or next Year.
At least nowadays it seems halfway affordable (Akitio Thunder and an older-gen GPU) and doable even for an average user to go eGPU. Whether it would make economic sense to spend that time and money for a machine that’s technically a couple of years old, is a different question, though