After the 31-03-2023 update some (or at least, the majority) of the applications I run using firejail started having the same problem: the keyboard stopped working, i.e., everything that I type within the application (Firefox, for example) was not been detected by it.
After some search I discovered that it is an old problem already discussed in Firejail github:
If you are having similar problem, it is easy to check if it is the same problem I am talking about. You only need to look at “.xsession-errors” and you will find several lines with:
IBUS-WARNING **: 02:56:39.905: Events queue growing too big, will start to drop.
The solution is simple. You just need to add “--nodbus” in the command line that loads your application (firejail --nodbus firefox, p.ex.).
Another solution is to include the two lines below inside the “.profile” file related to the affected application:
I hope that helps somebody.
P.S. Edit: included another option to stop the problem.