Is OCSP multi stapling supported by OpenSSL?
Still unsupported.
I think it still is not supported.
From openssl/blob/master/ssl/statem/extensions_srvr.c:
if (s-&gt;tlsext_status_type != TLSEXT_STATUSTYPE_ocsp) {
    /*
     * We don't know what to do with any other type so ignore it.
     */
    s-&gt;tlsext_status_type = TLSEXT_STATUSTYPE_nothing;
    return 1;
}

And from openssl/blob/master/doc/man3/SSL_CTX_set_tlsext_status_cb.pod

A client application may request that a server send back an OCSP status response (also known as OCSP stapling). ... Currently the only supported type is TLSEXT_STATUSTYPE_ocsp.