There's currently a check in `TransportService.HandshakeResponse.isIncompatibleBuild` to stop ES with the same Version but different build hashes from joining a cluster. This needs to be relaxed for cloud deployments where Version is not applicable
server/src/main/java/org/elasticsearch/transport/TransportService.java
private final TransportResponseHandler<T> delegate;
        private final Supplier<ThreadContext.StoredContext> contextSupplier;
        private volatile TimeoutHandler handler;
        public ContextRestoreResponseHandler(Supplier<ThreadContext.StoredContext> contextSupplier, TransportResponseHandler<T> delegate) {
            this.delegate = delegate;
            this.contextSupplier = contextSupplier;
        }
        @Override
        public T read(StreamInput in) throws IOException {
            return delegate.read(in);
        }
        @Override
        public void handleResponse(T response) {
            if (handler != null) {
                handler.cancel();
            }