Hi,
First, how did I not know about chessx before today?! I've only known about Scid vs. PC (and ok Chessbase a million years ago when I could still stomach Windoze). Great job guys, looks beautiful!
This is a weird one and it's no showstopper, and I'm not sure how you can reproduce it, but here goes.
I run Arch. I update it daily. I use the i3 WM. I built what was in the Arch AUR, so 1.5.6. Menus look fine on first run.
The only thing I've really tried to do (and succeeded), was load Stockfish, and load the big Caissa database.
Somehow every item in the dropdown submenus has turned bright red! I'm not really set up to screenshot these transitory dropdown menus but just picture bright red text with grey background. At best, it's painful to read. I'll attach a screenshot of what it looks like here but it won't show the red-text submenus I'm talking about.
I haven't seen this issue before, but every Linux Desktops tends to handle things differently and some do things in a weird fashion. So there's no way for me to reproduce these issues. Occasionally they can be fixed by setting environment variables in the desktop for Qt. I don't think, this is an issue which can be solved in ChessX.