I have similar problems as other with docker and collabora. I am getting the Collabora interface with turning loader and after a while an error message “that’s embarrasing”. I have one VM for Nextcloud with proper SSL cert from Letsencrypt and one VM with docker running also with proper cert.
I was able to connect all parts together, but I get one line of error in docker logs (nothing else like others) which is
ERR Error in client request handler: Timeout| LOOLWSD.cpp:996
I tried many configurations, now running on Ubuntu 16.04, I even tried to compile LO on my own and got the same result. It seems like something stupid, but I cannot figure out what.