After working in the Scala, which blurs the line between FP and OOP, daily for years, I feel like the choice to use OOP or not tends to boil down to how you'd prefer to solve the Expression Problem [1] for your domain. (if you follow the paradigm of "Functional Core, Imperative Shell")

If you're following this paradigm, for all your core objects they:

-Will be immutable, meaning calling methods on them will not change their state. (except for potentially some transparent optimizations, eg in-memory caching)

-Should not have methods that have side effects (i.e. purely functional)

If this is the case, then choosing whether your classes are objects or simple data structs is only a matter of code organization. ie do you want objects to carry around their methods with them, or have those functions live separately.

If you want to share method implementations among objects, you have the option of using inherited methods/types for a more OOP solution, or the typeclass pattern for a more FP solution. (Though the typeclass pattern has significant syntactical baggage in Scala)

[1] https://wiki.c2.com/?ExpressionProblem