I’m not a ruby code writer, but I read the document and find this:
Setting a Hash in <locale>.yml:
i18n:
transliterate:
rule:
ü: "ue"
ö: "oe"
So this is the way for customize transliterate in setting, at the end of function, we got Latin text (friendly url) only. I tried with my native language, and no need to define custom hash setting.