I have a touch computer. And when I activate the on-screen-keyboard it does not appear when I need to input something in Firefox.
(Keyboard appears when touching search box in "ubuntu software", prompting for password or using terminal)
If you don't necessarily need to use Wayland, switching back to X11 did solve it for me sufficiently.
You can do that on the login screen. When you click on your user, a cog wheel appears in the lower right corner. There you can switch to Ubuntu on X11 and log in. After that it was working again for me.
