Continuwuity. I'm using it. And contrary to other projects, it's a community effort. So I have my hopes up it'll last and not depend on any singular person.

And I wouldn't recommend Conduit or Conduwuit. Conduit development is very slow, that's why we got the forks in the first place. And Conduwuit is discontinued, so it wouldn't be wise choice at all. So you're left with 2 choices, Tuwunel and Continuwuity. One is a one-man show and they're calling it the "official" successor. The other one is a community project... They both work fine.

I use tuwunel. I'm happy with it. See no reason to switch.

Having a great time with Tuwunel, although it is deployed on and handled by yunohost, and my instance is text only. I wanted to try to set up voice calls, but the docs are going over my head-- it seems like so much to do in order to get calls working.

I've been using Continuwuity for a bit. Its pretty solid, but its not quite as smooth as Synapse in some ways. I've used several different clients successfully with it, but the pain of syncing the encryption is a real turn off. It needs to be MUCH smoother if matrix wants real adoption by non-techies.

Ive used 3 of the 4 and have been on Continuwuity for about a year, no complaints. 

I am also interested in the answer. I've tried Conduit and it was easy to deploy, but I had trouble with search and new user registration. Now I'm trying Continuwuity and new user registration still isn't working for some reason.