This FPGA passthru app, needed to program the ESP32 since is it not directly accessible, is written in VHDL.
Open the Diamond lpf project file:
Note that only 2 files are needed, the passthru.vhd VHDL code, and the ulx3s_v20.lpf constraint file.
Next, click on the Process tab, check the Bitstream File checkbox, right-click "Run all":
Once the implementation\passthru_implementation.bit FPGA binary file is created (or copied from examples/bin), it can be loaded onto the ULX3S with ujprog:
ujprog.exe Diamond_Blinky_Implementation.bit
For a more detailed example using Diamond, see the Diamond Blinky Example
See also other examples, as well as the Verilog Passthru