Tuya-Convert might not be possible for this device since the template was added (2019-11-30). All new Tuya devices have firmware preventing flash but it is still possible to Tuya-Convert old stock devices without connecting them to the Tuya app.
Flashed with Tuya convert. Start tuya then press button1 while plugin to poweron, keep pressed for 10s until led blinking. Retry 2-3 times if it doesn’t work at first.