For anyone wanting to expand their S21 storage, I recommend portable SSDs from Samsung. Smaller than a credit card, connects directly to your phone, and optional password lock encryption on the drive.
Samsung's security cam-ready PRO 256GB microSD hits new low at $40, more from $11
Amazon.com: Customer reviews: Samsung T3 Portable SSD - 500GB - USB 3.1 External SSD (MU-PT500B/AM)