This review is mostly accurate, and I understand why it's 3/5.

> The extension is proprietary.

This extension is open source, but I hadn't updated the URL since I migrated from Sourcehut to Codeberg. I have now updated the URL.

> It does not appear at the beginning of the address bar, as shown in the screenshot.
> At the end of the address bar, instead of the orange icon, as shown in the screenshot, a white square appears.

These sound likes bugs. If you file them on https://codeberg.org/tomf/boring-rss with screenshots and browser details, I can take a look.

> Doesn't detect feed links on google.com/alerts.

The extension only intends to find feed links if they're tagged appropriately. Please file a bug if this webpage declares its feeds in some standard manner, but the extension doesn't find it. I know other extensions will have custom code for certain sites, but this extension isn't going to do that.

> Does not display the type (format) of each feed found, but only its Title.

Fair. I am too lazy to implement this.