Gunboat is an awesome version of the boardgame -- no messages other than the moves on the board. There's plenty of diplomacy and careful deception involved.

Playing online through exchanging letters is slow (e.g. a week per game year), but it definitely has very serious deception and diplomacy.

I played a game of Diplomacy online where people started doctoring photos of texts and sending them to each other to spread misinformation. I started only collaborating with people over phone calls and told everyone I would not be making any strategies over text, so I could have plausible deniability about any fake photos.

Not true at all. It's different, but plenty of deception and diplomacy. I've played werewolf online as well (in forum threads, way back in the day) and it's quite similar!