Microfilm Is basically the only method that will work until the end of this planet when stored properly. Governments usually store important data on microfilm in deep bunkers.
Btw, a HDD technically can last forever as the stuff is physically written into the plate. The problem is accessing the data.
Magnetic tape drives are also a idea, they are slow and all but basically indestructible, same goes for the reader. You "just" need to make shure you have a adapter XD
And no, CDs are not the longest lasting. If you want to store shound forever, vinyls are your friend.
Digital storage is hard to preserve, make stuff physical if you want to have ot in many years.