keyboard becomes unresponsive in some applications

[robert marshall]

Since my upgrade to 20.10 I am sometimes seeing the keyboard becoming unresponsive (or very slowly responding) in some applications. At the moment emacs is in this state - menu events in emacs are fine. I've also seen this behaviour in konsole and firefox. I think the loss of keyboard happens after closing a window (but not always), so far I don't have a recipe for replicating.
I've seen bug #1912670 but I'm running plasma (and kde 5.74.0) and my mouse isn't affected - and the current hypothesis on that one is that it is xfce related.
In spite of keyboard not working, here I am typing (in the browser) without a problem. Sometimes when it is unresponsive I'm seeing a c5sec delay before the keyboard event is acted upon rather than nothing at all happening.

lsb_release -rd
Description: Ubuntu 20.10
Release: 20.10
I've just suspended the desktop and on un-sleeping the problem is still present.

There's no messages in stdout/err for the current emacs session. CPU doesn't look terribly busy. Suggestions on how to debug this are welcome!

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1912944/+editstatus and add the package name in the text box next to the word Package.

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[robert marshall (robert-capuchin)]

though it may be at a lower level (I wanted to enter kde-plasma-desktop here which I do have installed from Ubuntu)