Oh! Okay ,,Lately they been introducing more serbian in Holy Liturgy, but Keep part's ,in the Church Slavonic....
When i was younger and a altar boy ,it was all 100% church salvonic. other than the Gospel readings and other and the sermon...
Serbs most of the times two Liturgies ,english, and serbian/slavonic.....or combo serb/slavonic/ english
Myself i would never attend , all english serbian Church.......Our Hymns In serbian/slavonic just sound better also the whole service....
Hope this answer your question.....

Serbs will never abandon it's mother tongue , serbian/church slavonic in church completely.....there's room for english and even greek and other...

Is this in practice anywhere?
Not that i've see, it's usually the deacon if there's one, only choir or cantors that sing or chant the responses ,never seen the people {narod ] do it at the Liturgy... If that's what your asking....
I have no slightest idea to what question you were answering.

Anyway, I meant to ask whether the liturgy is celebrated in Serbian anywhere?