Any GNU/Linux Gurus. Need Help

GNU/Linux serves my needs except for paying some bills.

It seems that some commercial sites, for whatever reason, do not
interact too kindly with GNU/Linux versions of the standard browsers.

For example, try this link with a recent install of the Firefox
browser:

<https://auth.proofing.statefarm.com/login-ui/login?>

Don't worry.  You don't need a StateFarm account.  But the link
should produce a "Server Not Found" error which is inexplicable.

As I indicated, this occurs with GNU/Linux Firefox and also with
GNU/Linux Iron browser (based on Google Chrome).

<https://www.srware.net/iron/>

So why is this happening?  What is so different about the GNU/Linux
environment that causes this to fail?

I am forced to use Firefox on Micro$lop Winblows (yecch!) to access
this site and pay my insurance bills.

I encourage any readers of this post to try to access the above link
with a GNU/Linux browser and report the result.