You can change that setting via the actually lemmy instance page. For me I logged into lemmy.world and the settings there set All and New. That setting carried over into whatever app I used.

I tend to sort by new and all, and it seems like the majority is bots copying posts over from reddit, they have original link to the post on Reddit but there is the bot disclaimer on a lot of posts recently. Maybe it will die down a little once these bots move all the data from reddit to lemmy

I just switched over to lemmy from reddit, and it is much nicer here isn't riddled with ads and toxicity. I just hope that more users do join over here, since there were a few subreddits/people I followed and would still like to see there updates/posts