If you know how to do it on ubuntu, it should also work on Turnkey. Turnkey is a streamlined debian, and debian and ubuntu shares most of their codebases. What works on debian mostly works on ubunut and the other way around. Yo may have to install the necescary software on turnkey, but it should work.
Another solution is to skip the premade ISO’s, and use Ubuntu and this guide: https://minecraft.codeemo.com/mineoswiki/index.php?title=MineOS_(apt-get%2Bsystemd)
This would install the MineOS webUI on top of ubuntu.