This looks like the same bug I encountered when upgrading to 1.19.6.The system freeze is caused by some faulty logic that tries to use every device (including ttys) with the libinput driver.
I already reported the bug, you can find it here: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=889038
There is also a patch available and the issue is already fixed upstream: https://patchwork.freedesktop.org/patch/196090/
Kind regards, Hannes
