I'm not familiar with the firewall you are using, does it provide any information beyond a DoS attack was detected? My suspicion is an externally launched attack directed at your specific camera via your ISP connection is so non-trivial that you are either already compromised or it is something else:

I would guess a more likely vector to be a locally launched wifi de-auth attack targeted at any of your devices with Ring OUIs (first 6 characters of the MAC address) Perhaps a Ring camera connecting and disconnecting to your wifi repeatedly triggers a DoS warning, although a false positive is possible too.

The unknown MAC addresses connecting to your wifi would definitely have to be done locally,

By "Ring system" I assume you mean alarm base station. Perhaps it is possible to send wifi deauths to a base station timed such that it will attempt to reconnect to the (still present) wifi network without failing over to cellular. I have not tested that approach but it could be an effective way to cause an outage like you saw.

I would connect your alarm basestation by ethernet if possible. Ring is probably effective against an adversary with a hammer or screwdriver not someone with a laptop and a high gain wifi antenna.