I have a rooted Galaxy Note Pro.
I'm annoyed at black blocks that appear instead of whatever symbol, when reading web pages. I copied Code2000, Symbola, and the BMP Fallback ttf files to /system/fonts, but (e.g. https://en.m.wikiversity.org/wiki/Reed%E2%80%93Solomon_codes_for_coders#Finite_field_arithmetic ) I still see a block instead of the symbols for Real and Integer domains. This test page shows lots of blocks in Firefox. The Android browser simply skipps them instead. I also tried Opera.
Is there something needed to register ttf files, other than copying them to the directory? ( Total Commander remounts the file system r/w ) and rebooting?
It's annoying that I can display Tamil, Myanmar-extended-A, and other things I can't actually read, but am missing symbols and marks that appear in pages I do wish to read.