Sending logs to Loki

Hi,

in accordance with:
https://syslog-ng.github.io/admin-guide/070_Destinations/125_Loki/001_Loki_options.html
I try to send logs to my loki server

@version: 4.8
@include "scl.conf"

options {
    chain_hostnames(off);
    use_fqdn(no);
    keep_hostname(yes);
    dns-cache-expire(87600);
};

source s_internal {
    internal();
};

destination d_loki {
    loki(
        url("my.loki.ip.here:13100")
        port(13100)
        labels(
            "server" => "my-syslog-server",
        )
        template("${MESSAGE}")
        auth(insecure())
    );
};

log {
    source(s_internal);
    destination(d_loki);
    flags(final);
};

but always get:
2025-05-06 15:00:50.373 Error establishing connection to server;
driver='d_loki#0', worker_index='0', location=

Test requests through curl pass well (from syslog host).

Dump from tcpdump:
- from syslog-ng:
.U.Q...5PRI * HTTP/2.0

SM

..$.....................?.....?...... .................?..

- response from loki
...-.U.QHTTP/1.1 301 Moved Permanently
Location: /%2A
Date: Tue, 06 May 2025 11:56:42 GMT
Content-Length: 0
Connection: close

what could be wrong with my conf?

Thanks in advance.
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