manually port forwarding for my router

[AdamN]

What VPN did you use?

Playing over VPN is similar to playing on LAN, you can't use public adhoc servers like socom.cc or sushicat, so you need to use built-in adhoc server and connects to the adhoc server using VPN IP, this includes the one enabling the built-in adhoc server (ie. don't use localhost)

You can try following the guide at wiki https://github.com/hrydgard/ppsspp/wiki/...ith-PPSSPP

You can also ask in official PPSSPP Discord server (channel #multiplayer-adhoc) https://discord.com/channels/29331614147...1437818880
Some people in the channel said they can use Warp 1.1.1.1 VPN to connects to public adhoc server, but doesn't work on all games