Hello phseiff,
I just checked, and apparently, I still used texlive2017. It also looks like all texlive-related packages are at version 2017.something in the Ubuntu package repositories. I re-installed it now from another repository, and now I have the 2019 version (the same goes for tex4ht). I also noticed I had make4ht version v0.2e, so I downloaded v0.3f from the GitHub repository and installed it using `make` and `make install` (I hope that was correct). I can't run the new installation without sudo yet, though, since it seems I accidentally installed it as a super user; I will fix this tomorrow.
Ah, it is quite old distro. We added lot of features since then. See the full changelog: https://tug.org/tex4ht/changelog.html
Thanks again for looking into this and giving me this detailed explanation on how to solve the problem and why it arises; it's very much appreciated and helped me out a lot! :)
I am glad I could help. I should add some stuff from my answer to the documentation, because issues with \title are quite common.
Best regards, Michal
