Private Relay ane the Internet

About iCloud Private Relay - Apple Support (CA)

Learn how iCloud Private Relay—part of an iCloud+ subscription—helps protect your privacy when you browse the web in Safari.

Note: iCloud Private Relay is not available in all countries or regions and is currently in beta in iOS 15, iPadOS 15, and macOS Monterey.

This kind of speak volumes regarding the day to day general usages and reliability

Not an answer to your specific question, but I've always found the internet to be unavailable at times regardless of which ISP I was using at the time. And I've used many. It's just not perfectly reliable.

I'm sure you're going to experience interruptions with Private Relay, in the real world expecting no internet connection to ever happen is fantasy. The problem is it's difficult to tell what's the problem .... software, modem, router, cable, signal splitter .....