"A password reset request was sent..." System-level phishing?

I suggest changing your iCloud password and enabling 2-factor authentication if you haven't already. But DO NOT click the notification to do this. Go to Apple's website to do it. (Also, don't trust anyone on the internet to give you a good link. Check your URL bar to make sure you are at appleid.apple.com when you click even my link.)

Also, go to System Preferences -> Notifications and see what apps have notification access and restrict notification access to anything that looks suspicious.

Judging by the way the notification looks, it does not look legitimate as it does not have an app icon. You can call Apple if you want to make sure, though.

These messages can be legitimate. I'm on Big Sur and received the same notification. Shortly after I received a legitimate 2-FA code via SMS and a call with spoken code shortly thereafter. All these actions were not initiated by myself.

As a precaution I changed my password and tried went through the "forgot password"-steps myself to make sure this could be initiated without having my password. The good news is that these verification requests, texts and calls can be initiated by having only your e-mailaddress and phonenumber. So you can probably rest assured that your password is not compromised. Just to be sure, I'd recommend changing it anyways, as elaborately explained by user Salocor.