There are different software that could help this happen but I’m not sure how they’d handle all of lemmy’s content

There is Gun.js and OrbitDB (OrbitDB runs on IPFS using Helia)

and there is FreeNet which allows hosting of freesites on their network if you have something downloaded to your computer.

Some of the problems could be mitigated by volunteers running relay nodes hosting the kind of content they want to stay up (this would work with Gun.js and OrbitDB since it allows subscribing to specific data) or just general relay nodes that gives the network more capacity (this would be the method if you are working with FreeNet)

Again not sure how easy or hard this would be so I hope the developers share their thoughts.

Edit: When I say relay nodes hosting I don’t mean they have control over the data but instead keeps the data online. The data is still stored on the users own device and is shared between users if both are online at the same time.