What I did (last year) was to make sure they had at least read https://www.microsoft.com/en-us/WindowsForBusiness/End-of-IE....

IT only pushes back because the business users who use old web apps push back. Gotta make sure that IT knows the MSFT no longer has their back and so they need to be more aggressive with the business users and their app vendors.

It's their company on the line. IE6 is basically a giant security hole. Anyone using it on any system whatsoever is putting themselves at huge risk.

Those are extremely marginal as they're POS systems (+"Thin PC", I guess. I have no idea what that actually is.)

EDIT: I mean, I understand if you want to be able to keep using a JS/CSS framework, but it's not really reasonable to ask for upstreams to keep supporting such marginal systems.

Maybe find a link that crashes their computer through a remote-execution hole in their old, crappy browser.