With the huge variety of available FaaS platforms in cloud and self-hosted environments the idea of migrating function applications from one provider to another is becoming a important consideration. This work investigates the challenges developers encounter when manually migrating applications between Amazon Web Services, Microsoft Azure and IBM Cloud regarding the efforts needed to migrate the functions and the services. This work also proposes a simple approach to reduce the coupling between the function application and the cloud provider by externalizing the business logic into a serparate, completely vendor independant, package. We see that this approach reduces the efforts needed to migrate the source code to another provider but it does not reduce the effort of migrating the functions configuration and services. We see that the efforts for migration are not only affected by the migration of the source code but also by the migration of the services, especially in self-hosted environments. There developers also have to find a proper substitution of the service for their use-case.