The package correctly installs the fonts and creates the /etc/fonts/conf.avail/09-texlive.conf file. In order to have the fonts visible by the system however, for example to make Firefox able to read Latin Modern for MathML, an additional step is needed. Following the page at https://developer.mozilla.org/en-US/docs/Web/MathML/Fonts I created a symlink with "ln -sf /etc/fonts/conf.avail/09-texlive.conf /etc/fonts/conf.d/" and updated the cache with "fc-cache -sf". Now the system can see those fonts. I think Debian and Ubuntu do this by default, because I never had to do this in any of them. It's not a mandatory step, but I ask you to consider whether it needs to be default or not. In any case, thank you in advance. Reproducible: Always
Right, we could enable the TeX Live fonts per default. Note that there is also 09-texlive.conf installed by texlive-xetex.