The original TCP / IP method does not work for civ2. I do not know what it is connected with, perhaps due to the fact that this is a very old game. Until the end of last year, I used Tunngle and Evolve to play the game, but they were successively closed and are not working now.
Hamachi remains, but it works only on some versions of windows.
Regarding PBEM: I do not think that we need this for a normal game according to the original rules of civ2. Perhaps this only makes sense at the very late stages of the game, when each player has many cities and units. But, as practice shows, this game comes very rarely. How do you want to play, with what settings, what rules do you prefer?