In T6061#89530, @sicherha wrote:

Do Guam's log files, which can commonly be found under /var/log/guam/, provide any helpful clues as to what is going wrong here?

@sven.wtal erts-10.2.4 was indeed on my system. Glad that you found a working backup.
@SebastienWeber you're wecome

I'll have a look when I get back later. For now I just wanted to mention again that I'm using Debian so maybe my solution might not work at all un Ubuntu!

Hi Sven,
Ansible lineinfile only means to change one line matching the regex. So the file /usr/sbin/guam is not a copy of the executable but just plain text marked as executable:

Hello folks,
good news. I managed to restore functionality on my systems with a workaround. I just copied the old versions of guam-libs and erlang-eimap and adjusted it's executable /usr/sbin/guam . Afterwards login is possible again and iRony is working. The old and new versions will reside next to each other in the libs folder. Any update of guam will disable the workaround but leave the old versions around so we have to delete them then.
Unfortunately I'm not an erlang programmer nor understanding the whole architecture well enough to actually provide a fix for the most recent version.
But now that we know the bug is definitely in one of these two packages, maybe someone else can?
Have a nice weekend

I did some more testing with roundcube debug on: