PL/pgSQL is close enough in terms of language features to be nearly syntax compatible after some ora2pg-like transformations, aside from autonomous transactions

PL/pgSQL is close enough in terms of language features to be nearly syntax compatible after some ora2pg-like transformations, aside from autonomous transactions, which apparently are now supported by Postgres 11 procedures (I haven't tried this). Your main problem will be all the DBMS_* package calls... orafce helps a bit, but not if you've gone really far into Oracle-land. Procedures you wrote for DB system maintenance may not have a meaningful translation. Alternatively, you could pay EnterpriseDB.