> (I'm not sure /tʃm/ is valid in any language - words or names that start with "chm" seem to be Polish/Russian words transliterating /xm/.)
Oh it sure is in Croatian (and other Slavic languages), "tʃ" is written as "č". We even have slang words like "čmr-lji-ti" [t͡ʃmrʎiti]. "r" (rolling r) can function as a vowel.