Yes, you can remove flatpak and everything in it.
Open a terminal with the keyboard shortcut ctrl+alt+t
Enter in
flatpak list
This will list out all flatpaks installed. While it may look like a lot of things you need, you would only need them if you were running a lot of flatpak applications.
flatpak uninstall --unused
sudo apt remove --autoremove flatpak
sudo apt purge flatpak