Is it possible to print on custom paper sizes with an HP Smart Tank 519 without getting an E2 error?

Yes, it is possible to print on custom paper sizes without an E2 error, but it requires correct configuration. You must define the custom paper size in your computer's print settings (usually under Printer Properties > Paper/Quality > Custom or User-Defined). Ensure these custom dimensions are accurately entered and that the physical paper loaded precisely matches these custom settings. The printer needs to be told exactly what dimensions to expect.