I think that is a very urgent requirement! If I had known beforehand that an ISP connection is required to trigger the Ring Chime, I probably would have stayed away from the Ring Video Doorbell. Especially since hardwiring with existing non-ring chimes as fallback is not provided/possible in Europe.
Please make sure that a Ring Chime rings via local Wi-Fi even if the ISP connection is down. How else should e.g. the provider service technician ring when he comes to repair the ISP connection?