It's open-source and you must either self host it, install it as a program on your desktop or install it as an application on your phone or tablet. See the Downloads page.
Living in France too, what I ended up doing is setting my ISP (SFR) router in DMZ mode and forward everything to my own OPNSense router. Since I did that, I never had to interact with the ISP router again. I only need to use my router to manage my network.
Then, on OPNSense you may choose your DNS and it bypasses the one on the ISP router. Problem solved !