I've had this password protected 7z file sitting in my drive for a few years already now, and I have absolutely no idea what method I should use to crack it open. I think it should have between 12 to 14 characters, but that's pretty much it. I could use some help setting up a command that could brute force it without using wordlists.
If you don't know anything about the password except its length then you are left with the brute force method but in your case recovering a password of 12-14 characters on this 7z hash is virtually impossible. See how many hashes it breaks per second 14 cards 3090 = 14270.2 kH/s Simply put 7z has a very strong encryption algorithm.
bruteforcing 12-14 characters will mostly result in a bufferoverflow for hashcat as this keyspace is more than hashcat can store ( 2^64 is max ), so bruteforcing will not work, anyway, if it would work, it would take thousands of years as 7z is a very slow algorithm