Is it possible to use any custom Emoji set for mobile in order to keep brand consistency? [closed]

THIS IS ABOUT CONSISTENCY of the UX!

font-family: sans-serif makes the flag emojis ~rectangular on a PC, but on mobiles I cannot find a type which would give me country flags with straight edges. Everything is wavy. Is there a family with straight flags? Are there free OpenType or TTF mobile fonts which would do what I need?