feature request: option to toggle the usage of a mobile user-agent to circumvent meta's money ultimatum

[joostvhts]

Is your feature request related to a problem? Please describe.
Recently, both fb and ig forced an ultimatum upon their users: we were 'allowed' to choose between paying for their platforms or allowing them to use even more of their data.

Describe the solution you'd like
I would like the extension to have a feature that easily lets me use a mobile user-agent string only when visiting domains where the container is used, so that I can use facebook's website on my desktop by pretending I'm a phone. I'd imagine a toggle in a settings menu to turn on this feature, causing the app to not only contain the domain but also swap out the UA that my browser sends to it.

Describe alternatives you've considered
I've tried using a UA extension, but it wasn't that straightforward, and since I'm just a power user and not a developer so I couldn't quite find the right way to do it. Until now, I have been able to get around this ultimatum by using both platforms in a different way, but idk whether/when they will change this. The fb ultimatum only appears on the desktop site, while the ig ultimatum only appears upon opening the ig app while having an internet connection, so I only enable my wifi after opening the app, and presto, no ig forcing its will on me. So, using the mobile website is currently a solution for both fb and ig, but they prevent me from using facebook on my desktop.

Additional context
Feel free to burst my bubble if this feature is not practical or if it doesn't belong within this extension!! I have no idea how many people are currently still refusing their demands so it's possible that nearly everyone has already mindlessly clicked their 'free' option weeks ago. And thanks in general for all your work!

the ultimatum as shown on facebook's desktop site:

[ideologysec]

mozilla/multi-account-containers#2310