[lmm]

> It's unambiguous

On the contrary, if you just use the name of the language then it's not at all clear to a user who's using the "wrong" language where the language selector is.

[zapzupnz]

Then supplement it with a standard language switcher icon: either A/文 or a globe.

[lmm]

That will still be less recognizable for most users than a flag.