There are symbols from this table, which are not rendered on my system; as in, they're just rendered as vertical rectangles to mean I do not have the font to display them. This is the case, for instance, of U+26C4 which should be a snowman-like character, I guess, if I hover with the mouse on it.
If I want to have a unicode character correctly displayed, I think I should install one of the fonts listed here, but how can I know which one for each character?