I announced this in the Taleworlds forum, but not here, Steam Workshop, or Nexus. For that, I apologize. I released the 3.1 beta patch a long time ago in the same forum, because I wanted a small group of testers to iron out the bugs with the mod before I put it up here -- you all only deserve a tight bug-free experience. However, I hadn't expected to suddenly stop working on the mod, so only Taleworlds was left with 3.1 while you got nothing.
I'm not restarting work on Gekokujo right now, but I am going to rectify one mistake by linking you to the 3.1 beta patch thread (and uploading it as well). It is playable and *mostly* bug-free, thanks to the good people in the Taleworlds forum, but it is not quite up to the standards I think a patch should be before it gets released here. And most importantly, it's save-compatible with 3.0.
A description of the changes are available in the beta patch thread: Forums.taleworlds.com
1. Install Gekokujo 3.0 (if you haven't already)
2. Install the contents of the patch over Gekokujo 3.0 (this is the only step if you already have 3.0)
The patch is 41mb. If it is smaller than that, the download was corrupted and you should try a different mirror.