As "Sans Noto SC" etc only contain 27000 Chinese glyphs, and in some cases use 100s 1000s PUA characters, but many service need use these characters in application without correct font file installed, share U+FFFD or notdefined glyph shown the character make very difficult. Find method to solve Unihan display tofu problem, shown unicode in tofu. These method already done in many Linux system, but Windows iOS andriod need OS base method to distinguish the different characters. HTML also can done some effort.