Extracting Switch game files - hactool?

[Simpsons Dumper]

I'm interesting in ripping sprites, sounds and music from first-party Nintendo Switch games. It would appear that hactool is the thing to use, so I've tried using that to see what I can find inside the Super Mario Odyssey ROM. I now have three directories - normal, secure and update. Inside secure is a 5.5GB file (among others), which seems to be the one to try and extract. I've filled in keys.dat and tried using hactool on this file. It outputs some stuff (I don't know if it would be useful or wise to paste it here, but no errors) and Done!, but no files actually get created. Might I be doing something wrong?

Update: I found --plaintext can be used to create a decrypted NCA, but that's not very helpful as it's still not extracted.

[CHEMI6DER]

You're supposed to use --romfsdir=<path to folder where to extract files> to extract actual game files from an nca(an you were correct to use the 5,5GB nca, it is the game itself).