Why can't I see some chinese characters (eg: ) on macOS BigSur 11.2.1?
The display of any unicode character requires that your machine has a font installed which contains the glyph for it. Apple doesn't provide fonts for all 130000 unicode characters, so when there is one you can't see it normally means you have to download and install an extra font.
This page gives you a list of fonts that will show the example you give, U+26CCA.