Large white PVC pipe - about 10 inches across (whatever the big size is) with caps at each end, buried in the ground. Can’t burn, water can’t get in it.
Just remember where you buried it and make sure another trusted person knows, or write it in your will. Have some kind of mark that someone can recognize when they read description (or yourself - don’t forget where it is).
Safety deposit boxes are utterly worthless. Suppose the bank fails/gets taken over/there’s a bank holiday etc.
If a bank is taken over, it usually happens Friday after close of business, and reopens the next Monday, under a new name. Safe deposit boxes aren’t available around here on weekends anyway. As long as you use several different banks, it’s okay for most situations.
As far as where I keep my stash, I would not put that on the internet, where anyone including big brother could see it, if I were you. Now they know you don’t use the safe deposit box, and they’ll be digging up your yard.
Therefore, I am stating that I take my stuff to the safe deposit box, that’s my story, and I am sticking to it.LOL.