This would directly correspond to cass_schema_meta_version.

What cpp-driver means by server version, is the output of SELECT release_version FROM * system.local query executed on control connection.

The same release_version column is also present in system.peers. As a bonus, we could also fetch version information for each peer and store it in Peer and Node structs.

While it may not be useful for Scylla users because of scylladb/scylladb#8740 (TLDR; release_version is hardcoded to 3.0.8), it definitely is a nice feature to have for C* users.