Can you spoof UserAgent from header ?
Check on https://browserspy.dk/useragent.php
Not working on first visit.

There was an issue on Linux several months back that seemed to ignore some of the agent settings, but this appears to have been fixed. Thank you! Recommended, great extension.

So far it is working well. Thanks a lot! Finally i am out of request desktop site hell.

Doesn't Work on local file
Firefox Dev 71.0b7 (64 bits)

Cool!

Setting user agent for a window is nice. It'd better if it were persistent beyond Firefox restarts. Currently I have to set the user-agent for a window after Firefox started.