In my Collabora documents by default Dark Mode is enabled. Regardless of operating system settings or Nextcloud settings. This causes some problems with displaying uploaded files.
How to force Dark Mode to be disabled by default or (would be the best) disable it permanently?
What might be interesting in this context, though, is that there is now a separate toggle for inverting the document itself. This means that you can leave the interface in dark mode and still display the document in light mode, which should solve most of the issues that made documents in dark mode unreadable.
Unfortunately, at least as far as I know, it’s not possible to set either of these settings as the default, so perhaps someone can submit a feature request specifically for this: https://github.com/CollaboraOnline/online/issues