Not seeing upnp when on mobile network connection

On iPhone SE (2020) when on my local WIFI network I can see my rapsberry pi minidlna in Network - File Servers, when on mobile network with vpn activated I don't have listed any upnp connection. The key parameter is to be connected to some WIFI, because when I connect to any other WIFI network, which is not part of local network, but with VPN activated, then everything works ok. It doesn't work only when on mobile internet network. The same problem is on android and mobile network but on android I have found workaround - when on mobile network I turn on hotspot and then I can see my local minidlna in local network even on mobile data network. But for iOS, I can't find anything to make it work.

Simmilar issue reported here in this ticket but without any solution

Description

Expected behavior

to see upnp local server on mobile network with vpn activated

Actual behavior

not seeing upnp local server on mobile network with vpn activated

Steps to reproduce

1.disable wifi (mobile network activated) 2.activate wireguard vpn 3. if local server was already loaded in vlc app then everything works, if open application now on mobile network, upnp is not loaded

Screenshot / video

Context

App version

VLC for iOS, version: 3.2.13 (375)

Android version

Device model

iPhone SE (2020)

App mode

Smartphone