I need help with sober

Just on a general note: This forum is more about Flathub as a platform. Its not the best place to get help for specific apps. You can find links to specific help resources for an application on its app page on Flathub.org. Look for the Links section of the page, you can find links to help pages and issue trackers for the app there.

Anyways, that aside: The data folder for an Flatpak is not automatically removed if you uninstall it. GNOME Software will ask you if you want to remove the data, KDE Discover will not remove the data itself. If you use Flatpak in the Terminal, you should add --delete-data to remove that folder, such as:

flatpak uninstall --delete-data org.vinegarhq.Sober