The E6V2 has been available with either a bootmapper client or QMK powered PCB. During the second round, the QMK powered PCB was redesigned and used different ports and a different switch matrix.
Please use the appropriate version when making your firmware. Flashing one in place of the other, can brick your PCB. Please be certain whether you have a OE or LE PCB.
See [build environment setup](https://docs.qmk.fm/build_environment_setup.html) then the [make instructions](https://docs.qmk.fm/make_instructions.html) for more information.