The is no direct way to connect Oracle Forms to a non-Oracle Database. In order to do this, Forms must be connect to an Oracle Database that has the Oracle Transparent Gateway configured to access the non-Oracle Database.
So, the quick answer is no.
More on this;
While the official documentation doesn't explicitly state incompatibility with non-Oracle databases, it heavily emphasizes features specific to Oracle databases. Refer to the documentation for concepts like Oracle SQL and PL/SQL which wouldn't be directly transferable (
https://docs.oracle.com/en/middleware/developer-tools/forms/12.2.1.4/books.html).