That was deprecated in Mx7. There is an appstore module that does this functionality now.
If you want information on a topic for a specific modeler version then either state what version you are using in your question or select it when you are creating your question. If the latest version is not in the list, then select the version before it.
To move onto your point that Mendix should add a note or take down the link that you provided, you are referring to a community blog post from 2015, not the official documentation.
Here is a link to the official documentation.
In regards to your original question about wanting to use the sign in microflow functionality, there are other solutions that can be used to accomplish the same thing. If you stated what you are trying to accomplish, more information could be provided with alternative options.
Here is a link to a detailed blog post about autologin functionality which talks about transferring data from an anonymous user to a logged in user. I’ve used this method before and you can associate as much data as you want to the anonymous users session and that data will be transferred to the new logged in session when its created.
Matts website is currently down right now ( I will send him an email to see if its gone permanently or if its just having a technical issue) but luckily someone created an appstore module.
Regarding the after sign in microflow not being compatible with mx8, I’ve imported that module into a mx 7 project, updated the project to mx8, and fixed all of the deprecated api’s that are being used to accommodate mx8. I also created a test project to ensure the functionality is still working with the login form widget.
Here is the api’s that you have to fix:
OverwriteDefaultLoginAction.java line 33: replace core.addlistener with
anoUser = User.load(sysContext, oldSession.getUser(getContext()).getMendixObject().getId());
User signInUser = User.load(sysContext, newSession.getUser(getContext()).getMendixObject().getId());
I will be in contact with the module owner with these fixes so he can update the module at his convenience.
Hope this helps