flatbield

I am not sure any modified browser is that private since it is unique. Generally the whole point of a privacy browser is that you can use stock configuration.

Presumably combined with Tor or a VPN or multiple ISPs.

I wonder how it is deployed. If client side then uBlock Origin or NoScript might avoid.

Not sure there is. Dimensionality of the trackble elements is very high. All of them have to either be the same or fuzzed across large groups of users.