SHA256 is extremely FF-heavy, you need around 200k for an optimized, unrolled, pipelined implementation. UltraScale+ chips will run a proper design at 600MHz-8

SHA256 is extremely FF-heavy, you need around 200k for an optimized, unrolled, pipelined implementation. UltraScale+ chips will run a proper design at 600MHz-800MHz, big chips might be able to fit 24 cores. The Artix chip OP used is extremely slow and too small to fit this style of implementation.