@rafadobe
I think both of these are possible, we have worked on using the Source connector API to build a custom solution for one of our data sources. Here's more info for both
1.) Sources connector: Build custom connections from your data sources into AEP.
https://developer.adobe.com/experience-platform-apis/references/flow-service/
2.) Destinations SDK should help you build that connector.
The Destination SDK documentation provides instructions for you to use the Adobe Experience Platform Destination SDK to configure, test and release a productized destination integration with Adobe Experience Platform, and have your destination become part of the ever-growing destinations catalog
https://experienceleague.adobe.com/docs/experience-platform/destinations/destination-sdk/overview.html?lang=en