Note: A few very similar questions emerge in the search, but I believe the actual issues they address are different from the current one.
I have attempted configuration of DAV calendar and contacts synchronization through a new Android installation running the Nextcloud app and DAVx5. However, configuring a connection to the server account on the device fails. The application creates debug information that is quite detailed, but I believe the section describing the HTTP exchange illustrates the cause of the problem.
HTTP REQUEST
Request{method=POST, url=https://serverdomain.xyz/index.php/login/v2/poll, headers=[User-Agent:DAVx5/4.2.4-ose (2022/10/26; dav4jvm; okhttp/4.10.0) Android/12, Accept-Language:en-US, en;q=0.7, *;q=0.5]}
HTTP RESPONSE
Response{protocol=h2, code=404, message=, url=https://serverdomain.xyz/index.php/login/v2/poll}
Why would the address used to attempt login be reported as a missing resource by the server?
The server is Nextcloud 25.0.1. The client is Nextcloud for Android 3.22.3 and DAVx5 4.2.4-ose running on Andriod 12 as LineageOS for microG.