Thanks for the link. Well if you block googletagmanager you should be good from what I am reading here.
So what they are doing is instead of loading all the page trackers on your machine they load only google’ tag manager. If you block that one the rest won’t execute either.
Some more background:
The idea of google is that they are always the middleman. Gives them more data and the builder of the website more controls such as ‘GDPR settings’. The latter probably isn’t legal given the fact that loading google font’s as third party also violates the regulation (Google Fonts lands website privacy fine by German court • The Register).
But besides the GDPR aspect Google basically can act as a middleman if the developer chooses to. This ultimately gives the user and developer more control, however less transparency to the user who can no longer see what trackers are used unless this is disclosed. On the other hand it also makes it much easier to block tracking as simply blocking the tag manager would do.
I am however a little bit scarred reading this. It may happen that websites will start to refuse to load without the tag manager. Then we really do have a problem. There will not be anything we can realistically do against that.