Galaxy S9 Plus - Dual SIM & SD Card Work Simultaneously on Samsung Galaxy S9 Plus Duos - YouTube
Top things you need to know about the Samsung Galaxy S9's SD card slot | Android Central
Here are the best microSD cards for the Samsung Galaxy S9 & S9+
Amazon.com: Samsung 256GB EVO Plus microSDXC Memory Card for Samsung Tablet Works with Galaxy Tab S9+, Galaxy Tab S9, Galaxy Tab S9 Ultra (MB-MC256KA) Bundle with 1 Everything But Stromboli MicroSD Card
Does Samsung Galaxy S9/ S9 plus have a microSD slot