Another great option would be to use an FPGA, ideally a Lattice iCE40 (https://prjicestorm.readthedocs.io/en/latest/) -- or other FPGA with a completely open toolchain...
>Warning: Do not connect to any POE capable equipment!
What's the deal with this? I thought POE hardware always needed to "detect" attached POE capable devices before sending power.
That being said, my ubiquiti POE switch somehow managed to brick the ethernet port on my 1st gen Nvidia Shield so maybe it isn't that safe...