Yeah, it's sadly ubiquitous. I don't think a day goes by when I don't witness several sea lions in the wild

I've been running into something adjacent, but doesn't quite fit that description. Basically people use the tactics of Sealioning but the motivation seems to be just reframing the conversation to whatever they wanted to talk about, rather than necessarily pissing you off. It can be just as annoying though.

Sealioning is an accusation that rests on assuming someone else's intentions. You can't ever know for sure if someone is a sealion, because people aren't mind readers. I usually see sealioning accusations thrown by neurotypicals at autistic people, because they can't read our emotions like they're used to and that freaks them out and they assume hostile intent.

Sometimes people want to have a conversation without someone with the username DMmeYourNudes wanting to debate them.

Nope. That term is only used by sea lions and shitlords. It's one of those terms like "virtue signaling" that immediately lets you know the person has less to offer society than a common housefly or roach.

You've never spent any time on reddit, I take it?

That's a whole colony of sea lions.

Lucky you, but I encounter sea lions all the time. People like Tucker Carlson and Ben Shapiro have formed entire careers around sea-lioning.