Consul uses Envoy as its data plane proxy. Envoy would need to add support for SCTP before Consul could make it available.
I found this GitHub issue (envoyproxy/envoy#9430) requesting Envoy add support for this protocol. It doesn’t seem like there was a lot interest from the community & the issue has been closed. You may want to comment and/or +1 the issue to express your interest, or file a new issue with Envoy.
At the moment Consul does not force application traffic through the sidecar proxies. Your SCTP traffic can continue to connect directly to their upstream destinations. The proxy can be used for your TCP-based protocols.