Apparently, someone on WME and Tekno Discord managed to get WMMT6 LAN/Online VPN working. One PC needs to be running Terminal Mode with Terminal Emulator checked, while the other four PCs can leave Terminal Emulator unchecked and a Terminal Mode PC has to set to Event Mode and make sure all four PCs has to run at the same time until you see a screen with flashing red text. On the Terminal Mode PC, when it says that all four PCs are marked green, you have to select ready to deploy four PCs to Event Mode and now all four PCs can FFA with each other or 2v2.
The reason why LAN/Online VPN doesn't work is because Terminal Emulator option doesn't even function because both Jconfig and Tekno programmed to skip various bootup checks that involves Wangan Terminal unlike WMMT5.