Hello! Apologies for 4 year thread revival, but I ran into this same problem and it ended up being a crazy unexpected (to me) issue where the new windows and/or popups within containers were likely triggering the host KDE environment’s kwin to make a DNS request against the lxc container name. I still don’t know why this locks up the ENTIRE system, and it took me FOREVER to hunt down. But I realized it was likely a network-based issue when I found it did NOT occur while I had one of my network interfaces unplugged. That revelation led me to find the following issue in the “toolbox” repository:
The user in that issue post solved the problem by adding “toolbox” (the container name) to the 127.0.0.1 entry in /etc/hosts on their host machine. I found that as soon as I similarly added my lxc container names to my host’s /etc/hosts file, the problem ceased immediately. I assume this could also be solved in multiple other ways via DNS routing, but this solution seemed to be the quickest, and at least proves the “source” of the issue.
This was a very frustrating bug so I wanted to still put this here to assist anyone that stumbles upon this issue (as this thread was one of the first threads I found while trying to debug this).