I am registered at lemmynsfw, because I was looking for a moderated, but freely allowing instance aligning with my statement on sex positivity and wanting to see a tumblr like freedom regarding that.
However, lemmy.ml and feddit.de, two very large instances have issued a block. One of the reasons why feddit did it, was because the content would be mirrored on their servers and they would be legally liable for it for distributing adult material. The other being, the all feed will be flooded with porn as soon as some subcribe to it.
Why lemmy.ml did that is unknown to me, but shuts me out of a significant portion of the fediverse. Leaving me overall with little to no choice than to create a second account on something like this instance. And as far as I understand, even posting adult content on the lemmynsfw hosted communities would be a breach of the guidelines outlined on this instance, but I am not too sure about it.
Especially seeing the mirror problem, I doubt there is structurally any other choice than to have an advanced UI incorporating multiple different accounts for the lemmyverse.
The total lack of account portability makes these situations very frustrating to deal with, as the content has much longer half-life than microblogging and instance failures would have a large impact.
The iOS mobile app, mlem, handles multiple accounts fine in the app. If you are on iOS you can try it via TestFlight. You can switch between accounts easily on the account view.