I use Lyx in Xubuntu 18.04. Yesterday I installed a system update via the "software update" application, and now I cannot write x² in math mode because when I hit the key '^' instead of introduce the '^' symbol it seems to be introducing '\^'. I mean, this is what I get in Lyx:
and there is no way to introduce this:
using only the keyboard.
I have recorded a screencast showing the screen refresh problem in this link.