I'm not great with Wiki's Luc (I'm so old I started programming while we were just phasing out punched cards).
Actually, the debian package pretty much did everything on its own - it's case of
* Make a fresh install of DietPi (dietpi.com) for your SBC. (You're probably going to want a hard drive to.)
* Let it update, etc.
* Change the swapfile size to something a little larger - perhaps 600Mb (this is all available via DietPi's menus).
* Install YaCy from the debian package - that makes sure you get the right JVM.
* Optionally: link the YaCy store to the hard drive. I used a large (128Gb) MicroSD for my test.
* Stick a fork in it, it's done!
If you're using a Pi or similar, put a BIG cooler on that beast. There's a lovely metal case over at DietPi that will do the trick and allow the machine to throttle up to 1.2GHz 100% of the time without getting hot enough to keep your granny's feet toasty.