Copy 1, long term storage: LTO / LTFS is the way to go for one of your copies, it is by far the most reliable storage solution.
Copy 2, a big ass Truenas build, they can be done at the cost of the hard drives and can be configured for very high availability with 3 parity drives. Pro tip, have spare drives in the chassis but not configured as hot spares, it's a long story, you will learn if you go down the path of truenas. Get a used chassis for the drives and hook it up with a SAS adapter.
Copy 3, if you have important data, you will need a 3rd copy, and that should be LTO as well.

If you want more details, feel free to msg me