Is NetworkManager sending HTTP requests to googleusercontent.com?

You also need to take into account the 1st bit of that:

bc.googleusercontent.com

bc originates from Google Compute Engine (Google cloud) That does not have to be from Google itself. It is a service anyone can use.

177.143.198.104 is owned by NET Serviços de Comunicação S.A. Is that your ISP perhaps?

Some other services that are from Google:

lh3.googleusercontent.com Used for loading images for Google+.
lh5.googleusercontent.com Used for loading images for Google+.
lh6.googleusercontent.com Used for loading images for Google+.
s3.googleusercontent.com Used for loading favicons for AdWords ads.
static.googleusercontent.com
themes.googleusercontent.com Used for loading font files for Google Fonts. (Generally called within CSS from fonts.googleapis.com)
translate.googleusercontent.com Google Translation Service

Looking up the IP, I found this:

Hosted Domains  connectivity-check.ubuntu.com
                177.143.198.104.bc.googleusercontent.com

So it's an Ubuntu page hosted by Google.

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