Maybe, maybe not. Some manufacturers regard capacitor isolation as galvanic isolation. So measure it with a DC multi-meter and it will look like it is isolated. Unfortunately capacitors have exactly the opposite characteristics required from an EMC point of view, offering low impedance to higher frequencies. You really want transformer coupling or opto-isolation for true galvanic isolation. Only way to know what you really have is ask the manufacturer or open it up.
I am surprised your Waveshare seems to have blown up, I haven’t used that particular device, but many other Waveshare RS485 transceivers, never had any failures (Unfortunately that doesn’t really help you, sorry).
Much as I hate trusting what AI says, here is what the Google LLM AI concludes …
The conclusion that the TRENDnet TI-M12 lacks galvanic isolation is based on official manufacturer specifications rather than third-party forum summaries. The official technical documentation specifies ESD and surge protection limits without listing an isolation voltage rating or certifications required for a galvanic barrier. For further technical details, visit TRENDnet. [1, 2, 3]