For Firefox, see this KBA:
https://support.docuware.com/en-us/knowledgebase/article/KBA-35976
For Chrome and Edge, I'm sure there is a similar article, but I cannot find it.
If I recall correcty, You use the old "Internet Options" dialog o windows (Security tab) to add whatever address the client is supposed to use to reach the docuware server to "local intranet".