Icon emoji is a Unicode character rendered by font. So if you paste this to your html <span>🚫</span> the chrome-pdf should convert it to your icon. This works on Windows because there are required fonts already installed, however, on linux you typically need an extra fonts.
Here you can find demo with open moji web fonts used to render emoji.
https://playground.jsreport.net/w/anon/sLgBfpQB