After extensive investigation, we've confirmed that direct API uploads do not work on the 2018 Samsung Frame TV (UE55LS03N) with firmware T-KTM2DEUC-1341.2 and Art API version 0.97. All upload attempts via the samsungtvws library fail with error code -1, while the SmartThings mobile app successfully uploads images.
- TV Model: UE55LS03NXXC (2018 Frame TV, 18_KANTM2_FRAME)
- Firmware: T-KTM2DEUC-1341.2