You need to install a User Agent add on so you can change it on your computer. I use it all day long on my laptop with out the up sale page popping up.
This is the one i use for Chrome - User-Agent Switcher for Chrome
–user-agent=”Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-us) AppleWebKit/533.16 (KHTML, like Gecko) Version/5.0 Safari/533.16”
That or use a VPN and you won't have issues with tethering upsell redirect.