I have been running adult sites since the late 90s. The legal end is not hard if you have everything in order. I have it all under a media company with business insurance.
It is easy.
If I were to run a Lemmy NSFW instance I would have my lawyer write up the exact legal terms as PornHub, YouTube, and Reddit.
My system admin would also REX any banned words, flag accounts, and flag IPs; anything uploaded would be the user’s responsibility. I would also create a moderation bot.
His balls went into the shaft.