Oddbean new post about login | logout In both of your examples media came from a camera or a phone so there’s likely a backup. Yes people with default relays will have to figure out how to get around that, but at least there are options.
How do you get around it?
Make it less than trivial for users to host their own relays. A no-brainer relay on every device you own and one or two in the cloud. Extra points: users' sovereign relays also serve themselves their clients, so there is no trust problem.