Good

Easy to use. Facile et agréable utiliser.

the browser is now reflected as firefox 56 and google drive/site are complaining : not supported. after disable, it shows again firefox 92

I just tested your extension with this site: https://www.deviceinfo.me/ and surprise it's not that good.
Here is the response from the site "Supports real browser kernel detection even if the browser is spoofed, for: Firefox, Chrome, Edge, Internet Explorer, Safari, Opera, Konqueror."

Works wonderfully, would recomend.

Let me download Windows ISO with ease

AVOID!!! - causes PC to crash as "unsupported browser" tabs open - especially if using Linux + Waterfox as UA etc (more than that)

USE LINUX kODACHI

Does what it is intended. However, I would prefer if the user agent selection is somehow limited only to the tab where it was selected.