This one isn’t a strike, it’s due to planned construction/improvements along the line. There will be substitute shuttle buses available at Stade de France.
This is from Saturday morning through Sunday evening, according to what I just read. And the guy in charge said he thinks they will need to do this about 10 weekends in the upcoming year to get everything done they want to (!).
Also, Sunday 9/22 is the big annual car-free day in Paris, so there will be huge restrictions in place as to the kinds of motorized vehicles that are allowed to drive in a big swath of the city.