Fediverse isn’t for privacy or to get your content siloed, it’s main purpose is to … federate with other communities, send all of the public data to other servers.
If people don’t want that, they should use a good old forum, not a fediverse social network.
IPFS and then post a link through an IPFS gateway. Some browser resolve IPFS directly, I have one in mind but I don’t recommend it.