Hello, I am another potential Koken convert evaluating X3. Everything is looking great so far.
I might have found a small bug, but it could also be by design:
If you choose sidebar layout and narrow the viewport so that the logo moves to the top and the menu becomes a sandwich icon, then the footer disappears. As a side effect, clicking menu items results in "Invalid License www.photo.gallery" if you still use an unlicensed version. I could reproduce this behaviour with a fresh install of X3.30.1.min.zip and just changing style - layout to sidebar, both with Safari and Chrome on MacOS.