What does the organization say to do?

I'll email them and ask. I didn't see any info on their website about this.

https://azstrut.org/

They refurbish them..

https://azstrut.org/

Randoming out the data, replacing it with zeros. But some say they can still recover data.

Personally I'd be ok with DoD (Dept of Defense) erasure, then I'd probably pass a strong magnet from an old hard drive over it 99 times. As to whether it would still operate ....?

But then I've never disposed of a hard drive. They simply wore out from exhaustion.

To make hard drives unrecoverable.

https://diskwipe.org/ This is one of them. You can search for others but beware the ones that say "Free download" or similar. There will be a catch such as disabled features. You need to find true Freeware.