Samsung member App then click register
register your phone but might not register if your on a different firmware like EE, 3, 02, vodafone.
maybe only factory unlocked Galaxy S9 can get Android Pie Beta. if so then you need BTU firmware details can be on XDA web site.
US was the first ones to get android Pie follwed by Germany 2nd.
someone ask the Germany and US community how they got Android Pie Beta
ask them do we have to register our phone on Samsung Member app and do we need a factory unlocked phone or unlocked firmware (BTU)