Gluetun
This is pretty interesting, I never used that before and I will have a look. However, it would be also interesting using my approach, use a local interface where the traffic is already filtered, that can be used on other scenarios.
There is probably something on a docker configuration telling that all my traffic should go out from the default interface.
Not sure why you say that, all projects I'm seeing they ALL include FOSS, sometimes they just specify if one is European and another one no. Also, and to be fair this is the main reason your post make no sense, there is not only software but mainly services and goods as core part of the projects.
My opinion is that the US already has access to Apple devices data. If we consider this to be true, what the UK is trying to do it's to match a possible enemy capabilities. Is this a valid point though? This woudn't make this action less wrong, I must to be clear, but it would be more undestandable.
This is specifically for the public sector. The fact that it is open source make it adaptable to different scenarios.