GIVEN I am successfully logged in on the desktop site, e.g. https://www.wikidata.org/
WHEN I open the mobile site, e.g. https://m.wikidata.org/
THEN my logged in status is not detected and I can not make use of it
When opening the mobile login page, e.g. https://m.wikidata.org/w/index.php?title=Special:UserLogin&returnto=Wikidata%3AMain+Page&returntoquery=, the requests that try to facilitate the login can be inspected.
Apparently requests get sent against login.wikimedia.org but are answered in a wrong way for the wikidata domain - the Location header instructs our browser to connect to "https://www.m.wikidata.org/..." which is incorrect (stray "www.").
Applies to both production and beta.