To the best of my knowledge, PSL (whose last release, from 2010, can be found at
https://gitlab.com/YottaDB/DBMS/YDBPIP) is the only OO language that compiles into M. It is not supported by YottaDB.
There are multiple language APIs which are supported by YottaDB (
https://docs.yottadb.com/MultiLangProgGuide/), and some that are indirectly supported, such as C++ (which can call the C API directly).
Regards
– Bhaskar