>As a thought experiment, i've wondered what would happen if webdevs started to add those ugly "This website does not support Chrome, please install [Firefox](...) for the best experience."

I use Chrome for exactly one reason: adding shortcuts to websites as an app. Firefox at one point had (very broken) support for this, but they've since removed it (on desktop, it's still possible on the mobile app).

It is simply untrue that Firefox gives me the best experience. If you're going to block Chrome because of web privacy ideology, then just say that. Don't lie to your visitors. Telling me Chrome "isn't supported" is obvious hogwash. Instead you should tell me that you have blocked it, and why you have blocked it, and maybe then I would consider opening your page in another browser.

Strong arming users with false pretenses is deplorable, no matter which side is doing it.