Ralkage We have all the flags we need you fools ?
Oh, I see you inserted the Unicode entities. This way, the character π§π· is translated to the emoji ??, which in contrast to the unicode character looks the same on different platforms (and also better i.m.h.o.)
I assumed the brasil flag missing, because the Emoji code :br:, which is offered by the Emoji Picker, doesn't translate to the Emoji (as you can see :br: here). The same holds true for the :in: code for India. For everyone missing some of the flags: Try :flag_ and then the country code, so you will find :flag_br: and :flag_in: too, and they work.
By trial and error I just found out, that also :brazil: and :india: work for ?? and ?? too even though the are not offered by the Emoji Picker. ?
Whatever, if this list is complete, it looks like the best option for a Flarum extension.