Just a little bit education, so you and if you ask questions the people trying to help you don't get confused.

Flatpak is just the format. There can be many different independent stores. A store is a place where developers can upload their program with description and ready to install. Flathub in example is such a store, and the most common and popular one. Then there are applications who manage the download and installation from Flatpak. Discover is such an application in example. You can add other Flatpak sources, Flathub is most of the time already setup for you to use in Discover (and other apps).

I just use the commandline, which is the most efficient and fast way. For looking up I can still just use the Flathub website, and then use the commandline to install, remove and update the Flatpaks. But you need to learn and understand how terminals and commandline operation work (which isn't a bad thing to learn anyway.