The Titan Launcher has been updated to 3.8.0, all you have to do is start it and it should update on its own. That means you can now play 1.13 and 1.13.1 without the need for this tutorial.
One thing I am not 100% certain about, is whether you only need to get the launcher updated after doing the tutorial. My fix wasn't perfect, there were sound issues from 1.13 that passed over to 1.13.1 if you did the sound fix. I don't know if these will be sorted out by the update, and I'm unable to check as I deleted everything to make sure there were no more issues, so if you still notice sounds/subtitles missing, delete the assets, 1.13 and 1.13.1 folders (the paths to them from .minecraft should be .minecraft/assets and .minecraft/versions/1.13, respectively .minecraft/versions/1.13.1). The launcher will download everything needed properly. Keep in mind that 1.13 version has a few missing subtitles on it's own, nothing you can do about these. 1.13.1 has no sound issue that I noticed.
I'm gonna leave the old post here for "posterity", and maybe it's gonna help for later versions.
Edited by Astelon, 23 October 2018 - 03:44 PM.