In centos8, after you installed the Collabora Online following the official documents, it may not works fine when you open a file:
Collabora Online: Cannot connect to the host "https://office.***". Please ask your administrator to check the Collabora Online server setting
This may due to that the DNS in dockor is not work fine. you can check it by:
docker pull library/alpine docker run --rm -it alpine ping -c4 18.104.22.168 docker run --rm -it alpine ping -c4 www.baidu.com
if can ping IP , and can not ping any Domain, that is the DNS in docker are droped by the firewall in centos8.
firewall-cmd --zone=public --remove-interface=docker0 --permanent firewall-cmd --zone=trusted --add-interface=docker0 --permanent firewall-cmd --reload
instead of disable firewalld.
I am glad to hear safer solutions.