Recently upgraded to SharePoint Server 2019 from 2013 Foundation. All seems to be working ok in Chrome, but when in Edge we can only log in using DOMAIN\username format, otherwise we get constant login prompts. If you cancel the prompt it gives a 401 error.
Note that we log into Windows via local domain AD authentication. The SharePoint Server is on an external domain. However, both ourselves and external users are having the same issue with Edge, but I don't know the external users local authentication setup.
We authenticate via Claims NTLM.
We have tried disableloopbackcheck in the registry.
When logging in with the DOMAIN\username format, some functionality of the websites are lost, such as clicking on Edit Page or Site Settings being unresponsive.
I hope I've provided enough info, but please ask if I'm missing anything.
Any help would be appreciated.