I think that if, in good faith, the person is unable to accept more CSAM due to the fact that their hard drive is full, there isn’t an issue. The intent of the law is that, it someone knows something is CSAM, they need to report it. I don’t think the government is going to come hard on Lemmy server owners unwittingly receiving CSAM through federation (though they certainly would want them to report and take down the CSAM on their servers)

Be careful with this though. I think I remember some jurisdictions require server owners not to delete CSAM and report it instead. Verify that you aren’t obligated to keep it before deleting it

I would like to see a connection to PeerTube. I’m not exactly sure how it works but it might work here