This seems to be a one-way integration. I can control the device from ST, but when it is manually turned on or off with the physical switch or the SL app, it doesn’t update ST.
My device is a fireplace controller https://www.amazon.com/gp/product/B07WJSYBMK/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
It’s still better and faster than IFTTT!