OPPO s33 has no karaoke function. Find all four pages, as well as plug-ins such as constellations and calendars. It may be overwritten by other plug-ins. Look carefully. There should be, but I can't find it. Go to the store you bought or download the firmware from OPPO official website and give you the address.
/? Q = Software/View & ampsw_id=44
I hope my answer will satisfy you, thank you!