If somebody wants their FPGA work to be available, they better choose MiSTer FPGA from the beginning. Costlier, but way more likely to be found around.
My system version instead runs on RISC-V, so no custom FPGA implementation, currently on an emulator, but eventually on the ESP32 (which has a much better availability).
Well, the MiSTer project was yet 4 years from being launched back in 2013 when the RISC-5 was implemented in FPGA, so I hope you'd excuse Wirth from not choosing it.
FPGAs were never that maker friendly, due to the whole ecosystem.