According to F1 Documentation, Oracle 19c RAC is verified on both IFS Applications 9 & 10. Up to 4 RAC nodes are supported (with acceptable performance) for IFS Applications.
My Advice: Try to avoid RAC… it add complexity and you might end up with performance issues that very few DBA’s can sort out. Even if IFS can run in a RAC environment it is not a good fit as we have so frequent data updates (OLTP DB).