Lemmy does not have any kind of builtin "safeguards" against bots or scrapers (other than during registration, but I wouldn't call them safeguards). Some instances do use tools to slow them down or block them, such as Cloudflare or self hosted proof of work CAPTCHAs (for example Anubis, the anime girl).

While I can't say that bots are common in Lemmy, I do see a few of them in this comm and ban them every once in a while.

TL;DR: no builtin safeguards in lemmy against scrapers.

only email verification, captcha and manual approval against bots during registration

edit: clarified a few things