https://github.com/bitcoin/bitcoin/blob/d72758c3f6c34cd835f5de3efc230964f3b1ea56/src/torcontrol.cpp#L539

If a user is running Tor proxy outside localhost (perhaps on other host inside LAN or in containerised environment) , the automatic creation of onion services ends up creating an onion service listening to hardcored 127.0.0.1 address on the Tor proxy's host instead of the private address of the bitcoind – effectively running an empty onion service listening the Tor proxy's localhost.
{
    if (!g_upnp_thread.joinable()) {
        assert(!g_upnp_interrupt);
        g_upnp_thread = std::thread((std::bind(&TraceThread<void (*)()>, "upnp", &ThreadMapPort)));
    }
}
void InterruptMapPort()
{
    if(g_upnp_thread.joinable()) {
        g_upnp_interrupt();
    }
}
void StopMapPort()
{
    if(g_upnp_thread.joinable()) {
        g_upnp_thread.join();
        g_upnp_interrupt.reset();
    }
}
#else
void StartMapPort()