It’s technically possible to connect OneDrive to SharePoint 2019 on-premises, but it’s not simple. This setup requires a lot of technical knowledge about SharePoint and how the authentication works. Microsoft focuses on making OneDrive work best with SharePoint Online, so getting it to work with SharePoint on-premises can be tricky. Since you’re using Keycloak, the setup might get even more complicated. I recommend reaching out to Microsoft support, as they can help guide you through the process or suggest other ways to make it work.
