The obvious ones are simple repost bots. They start with 1 account reposting some popular submission, then you’ll likely find at least 1 or more other accounts in the comments reposting a popular comment from the original post. They typically are created at the same time and have a similar pattern of maybe a handful of comments and submissions. When I was still using Reddit I saw them all the time on /r/all. Nowadays you also find a lot of bots reposting someone else’s comment in the same chain, maybe with slight grammatical changes. There’s some people and even a bot account that call those accounts out. I’ve seen a metric shitton of this happening since the last big shitstorm (which also really changed the content on /r/all for the worse).

I think LLM based ones are probably harder to spot because they would sound a lot more natural and their profiles would look more organic.