This is an interesting FPGA project: https://www.crowdsupply.com/agilmine/ultraminer-fpga
It’s 100% dedicated to mining. No GPIOs (that I can see), no external interfaces other than a (relatively) low-speed USB (probably 2.0) port.
I’m not planning on getting into crypto mining, but the board might be an inexpensive interesting to prototype larger hardware designs and then move to a board with I/O later.
UPDATE: It failed to meet the funding goals. It didn’t really get a lot of hype, and it didn’t seem to appeal to serious crypto miners because it didn’t seem to be competitive with high-end FPGA cards in terms of payout/watts.