If you want to have a GUI method to check files for their hashes (SHA256, MD5, etc) first install Collision flatpak and then the Gnome Files extension to have a right click menu action.
For the extension you have to download collision_nautilus.py and copy it into the extensions folder:
curl -LJO https://raw.githubusercontent.com/GeopJr/Collision/main/collision_nautilus.py
mkdir -p ~/.local/share/nautilus-python/extensions/
mv collision_nautilus.py ~/.local/share/nautilus-python/extensions/
Then restart Nautilus
nautilus -q
It should then look like this:
