Are you talking about when Firefox starts or the home page?

https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

Type about:config<enter> in the address bar. If a warning screen comes up, press the I Accept the Risk button. At the top of the screen is a search bar. Type browser.startup.homepage

What is the value? Right-click and select Reset to restore its default value; about:home

Same on Windows. I think that site might be obsolete. The fact that it is set up only on HTTP rather than HTTPS makes me think it hasn't been updated for a long time. The console shows it tries to retrieve from links that no longer exist.