boost::beast is a header-only library. While boost::beast heavily depends on boost::asio as a networking library, asio is also a header-only library.
Therefore, typically, you don’t need to link boost::beast at all.
The only exception is if you are using SSL/TLS functions for HTTPS connections, in which case you need to link the OpenSSL library which provides the SSL/TLS layer. In that case, link it using
-lcrypto -lssl