@L4s@lemmy.world's operator here, and I'd be more than happy to answer any questions you have.
Like the majority of content bots on Lemmy, L4s utilizes Reddit for its posts, and I've been working on adding a few RSS feeds to branch things out more and better abide with the newer bot rules.
As for "choosing" what to post, it currently checks the most upvoted posts for selected subreddits and the up/down vote ratio, then if it matches the set threshold it will check if it has posted that link before, as long as everything lines up it will post.
Initially I had it set to once an hour on this community, things here gained a lot of traction a month later so I scaled it back to every other hour. In the near future I will be limiting it again to every 3 or 4 hours as we have continued to grow since last months decrease in posts.
As it says in the bio, the goal with L4s is to jump start communities, it won't be here forever. If you have an issue please let me know!
Also thanks for the tag @krayj@lemmy.world!