When migrating to a new system or OS, you'll have to install all the fonts that your documents use on the new system. However LibreOffice does not help you here:
1) When a font is missing, LibreOffice uses a different font (Courier?) _without_ any message showing up.
2) There is no built-in "list used fonts" or "show current font replacements" (fonts that LibreOffice silently replaced by other fonts)
So I suggest:
1) Implement something like a LibreOffice "Console" that can show informational messages or warnings when the user wants to look for these (would also help debugging and problem reporting, I guess)
2) Indicate if some fonts of a document opened are missing
3) Allow the user to list all fonts a document requested (I'm not using the word "uses" here, as the fonts could have been replaced already)
4) If 3) would also indicate missing or substituted fonts, it would be great.
5) You can print the styles your document uses (that function is hidden extremely well). I think the fonts a document uses are also a part of its style and should be included as well, possibly also with all sizes of the font being used.
Not disagreeing with any idea for improvement, but you know that on the tab Font from the dialog Font it _is_ indicated (above the lower box showing the result with the font) if a specific font is not available?
Very similar to bug 78186.
*** This bug has been marked as a duplicate of bug 78186 ***
(In reply to comment #1)
When opening a document in read-only mode that information is not available, right?
(In reply to comment #2)
Actually I think bug 78186 is only a subset of my proposals.