When you talk about necks, do you mean the fretboard, or the back of the neck?
I'm assuming the fretboard because you mention ebony.
You wouldn't normally lacquer ebony. Just apply either lemon oil or mineral oil (the sort that's designed for seasoning chopping blocks) from time to time to stop the wood from drying out. It will also make the wood look darker. Whilst I've never encountered it, ebony can split if it gets too dry, whereas rosewood is unlikely to, so it pays to keep it oiled (6 months to a year should be fine in Austria). But ebony is harder and has a much smoother surface with very fine grain, so that's why a lot of people prefer it to rosewood.
Your ebony fretboard will be lighter and have some figuring than the traditional black ebony fretboards that were the norm. Most ebony isn't in fact black, but people just wanted and used the black wood from it, throwing most of the rest away (which is one reason there's an ebony shortage). If you are trying to match a look of another guitar, then by all means stain it black. If not, I'd keep it as it is. I like the look of figured ebony.
If you are also talking about the back of the neck, then it really is best to have some sort of finish on there. even if most of it is sanded back. The wood really needs to be sealed to stop it absorbing or loosing moisture with changes in temperature and humidity as this can cause the neck to move requiring frequent truss rod adjustment. Even a light coat of something will provide more protection than nothing. A lot or people like using Tru-Oil, Tung Oil or Danish oil for necks as it gives a smooth feel. These are all 'polymerising' oils (made from linseed oil or similar) that basically form a resin/plastic coat as they dry. They are also very easy to apply.