Public Network and you don’t Use VPN? Smart.i think it was already in france last time you played Varadin.
Me it happened the reverse thing,
i changed location and i am now on a public network with wifi = shitty connexion,
but in M & S i play now with less ping than when i was at home with ethernet and a box, wtfff ???
That you have a lower ping on public wifi says enough to me. Anyhow probably you have a different ISP and firewall is different. Too many variables to conclude one thing but I highly recommend a Vpn for public networks.