While traveling by train into and around Paris, How have you gone about finding a place for luggage storage?
Some of the train station have lockers. I flew into CDG at 6 am and was leaving from St Lazare Station (no lockers) at around 6 pm. I used a City Lockers location near Notre Dame as a friend and I explored Paris during the day. The company has locations around the city. I paid for the locker -- they sent a code for the door and a code for the locker by e-mail. Super easy and worked great. https://www.citylocker.paris/en/
Lots of options in Paris.
https://www.france-hotel-guide.com/en/blog/store-luggage-paris/