Which gameplay mechanics? Not being smart, I'm honestly curious.
Being currently version 0.198, you can bet Daggerfall XL is far from complete.
Just look at the next version's description:
In Progress Now
Working on Version 0.20 Features starting with "Leveling".
In my opinion, a lack of leveling is a pretty big missing gameplay mechanic. Looking a bit further, it seems bows don't work yet either.
Honestly, for a Pre-Alpha version it would be quicker to list the things that do work rather than the missing ones.