The Ostfriesisches Teemuseum is the right place to start in Norden because East Frisian tea is not a decorative detail here. It is a regional habit with rules: strong black tea, rock sugar, cream poured without stirring, and time taken over the cup.
The museum sits in the old town hall on the market square and covers tea trade, porcelain, domestic rituals, and the local ceremony itself. Try to time your visit for a tea demonstration if one is offered.