I’m not sure if this is a Nextcloud thing or a Collabora thing, but I think it would be helpful to have a sample preview of the different fonts in the Document selection box before just picking and changing the font to see the result. There are a lot of fonts in there but many will never get used if the user doesn’t know what it looks like without selecting it first. Maybe there is a way to do this and I am missing something.
That seems to be a Collabora related request.