When I enter a unicode character (U+2611) into a cell which has a Liberation Sans format, sometimes the character is displayed as a plain box with a check mark but sometimes it autocorrects to a blue cartoony box with a white check mark. Changing the fort for the autocorrected blue check box to DejaVu Sans converts the character back to a plain black check box I would expect the behaviour to always be the same rather than the character sometimes being displayed one way and sometimes the other when the cell formatting is identical as far as I can see.
When I use: Insert > Special Character and select font "Liberation Sans" and enter 2611 into Hexadecimal, the dialog box says "Missing character" But 2611, Alt+X will produce ☑ in a cell formatted with Liberation Sans I am speculating that the "Missing character" maybe significant here. @Stuart -- maybe you can give some insight here?
Liberation Sans does not contain a glyph for codepoint U+2611 'BALLOT BOX WITH CHECK'; this requires os/DE font management to apply a font fallback. That is not controlled by LibreOffice. This is normal expected bahavior. To exactly control the result and avoid fallback handling, identify a font [1] [2] actually containing the glyphs desired and format the cells character assignment to match that font. Remember to embed the font if sending the document to others that may not have it. =-ref-= A Unicode character map program is most helpful to review with, look for a font coverage utility to show the fonts holding a desired glyph. [1] babelmap - https://www.babelstone.co.uk/Software/BabelMap.html [2] gucharmap - https://wiki.gnome.org/Apps/Gucharmap