As per the first discussion in this Reddit post in the LibreOffice community, I created a Github issue in Template Manager repo. As per the second discussion I created another Github issue in Flatpak repository.
Meanwhile, the Template is not showing in Template Manager. Where did things go wrong?
Distro: Ubuntu 19.10
LO Version: 184.108.40.206
TLDR; i) Installed LO from Flatpak ii) Installed the template using `sudo dpkg -i libreoffice-impress-templates-all_2.2-1.deb iii) Launched LibreOffice Impress iv) Open Template Manager. v) Didn't saw any template which I just installed.
But those template resides in the folder as you can see sadly in repeated form.