Future builds have versions of core, rpc, and horizon that should support protocol 21, so the local should default to running that protocol version. The only reason to have a lower version is if all the software doesn't yet support the latest because then startup of a local will fail with the default protocol version.
What
Set the default protocol version to 21 for future
Why
Future builds have versions of core, rpc, and horizon that should support protocol 21, so the local should default to running that protocol version. The only reason to have a lower version is if all the software doesn't yet support the latest because then startup of a local will fail with the default protocol version.