I will try test more using Oracle a virtual machine over a lan.
I had tested a short time with a german player over internet about 10fps it was acceptable though and playable like on Kali using the Windows version :-).
I did wonder if you knew about this bug that causes an out of sync in the original Dungeon Keeper and also KeeperFX a problem with the allie on the game menu, when for example 2 players allie with each other in the game menu. When 2 players are playing against the AI, for example on the multiplayer level 150. If they allied using the multiplayer game menu shown in the screenshot I attached of the game menu where my mouse cursor is, the game risks going out of sync in allot of maps. This used to happen to me on lots of games until I figured out what it was in the original.
If player 1 for example digs to the gems on level 150, once the boulder trap starts there the 2nd player seems to crash in KeeperFX if they allied inside the game menu before start.
I have attached the crash log also in case it helps. I know it's to do with the allie before the game starts. But it seems to be fine if they allie with each other when inside the game instead then there is no oos or crash.
The original will just load back oos message and try to get in sync again but only if allied inside the game menu.