Using E340 video doorbell with exiting wired chime

Has anyone succeeded in doing this? I have ween trying on and off for a couple of weeks without success. the sales bumf says that this IS possible, but although there and a few claims of having done this, and the Eufy website shows wiring diagrams for wiring to existing mechanical chimes, I have not succeeded.
Some of the Eufy support workers say that this IS possible while others say it IS NOT. ALL Eufy support team are very vague and unable/unwilling to provide detailed circuit diagram with a definitive statement on what IS and IS NOT possible.