In Edge runners, they were putting people's cremated remains in stainless steel capsule, like a world's worst kinder surprise. That struck me as being very plausible in the future.
My plan has always been to get cremated and then just bury my ashes somewhere with a little gravestone. No need for a container or anything, after a few years go ahead and bury someone else's ashes in the same spot and either replace the headstone or figure out a way to stack em. Just have a running tally of names and dates for everyone buried in that plot.
My plan A was similar. Just get cremated and just be scattered around my parents graves. Just so "I'm around“. Plan b, viking funeral. Plan "c" is getting cramated, getting an half and ounce of ashes, putting it in resin keychains. Then during the memorial, "take a little piece of Bob with you.", and hand out the keychains. Eventually, you are going to lose it, go back to my wife, because she probably has a box of leftover me somewhere.