Lunar is including an update of the Ubuntu-fonts. One of the change has been been the renaming of the ttf to be compliant with the googlefont guidelines.
Local testing showed that the filenames change is creating issue in the active session after the upgrade (already loaded programs are using a ttf which is removed from disk and not available in the fontconfig cache anymore which leads to all the chars turning into squares). To workaround the issue we added symlinks from the old names to the new name.
It’s non ideal though and is leading to issues, for example having duplicates entries in gnome-font-viewer. Poking around it seems we could perhaps ignore those with a configuration using for those entries? I’ve proposed a change that seems to work there but I’m not that familiar with fontconfig and its configuration and it’s late in the cycle so I would welcome a review of someone who knows the topic better.
I added a comment on a detail to your merge proposal.
But…
Is the only reason for the symlinks to avoid that issue in the active session, while all is fine after a reboot? If so, are the symlinks at all necessary? I mean, upgrades of Ubuntu version always include a reboot, don’t they?
Well the issue is that the text is the active interfaces is replaced by squares when the font is unpacked and the font cache update, which means at some point before the installation is done you would have a buggy desktop and you might not be able to read what the dist upgrader is telling you at the end of the upgrade nor to now how to restart…