If I understand correctly, the Lattice ICE software can't do JTAG, it will only program a SPI flash.
I don't see any pins on the iCE40HX8K marked as JTAG pins (even in the Lattice documents), however there's a JTAG option on this EVB!
I don't see a note about it in the wiki - could someone enlighten me?
Also the datasheet of the iCEdragon Evaluation Kit (by Lattice) features a schematic that shows some pins with their JTAG signals named like R14 - PIO1_00/TDI; R15 - PIO1_01/TMS; P14 - PIO1_02/CLK; P15 - PIO1_03/TDO; N14 - TRST_B.
We often put such options in our boards, they might never be used, but if we have free space available, why not provide this option? Maybe nobody would ever need it, but in case somebody does need it - there it is.
Thank you, that answered the question wonderfully and I'm glad I asked!