How to get multiple records from another table to the first one?

Question

MySQL

Hello! I met on some sites a feed of posts, where a few recent comments are displayed right in the feed under each post (conditionally 3).
Of course, comments are stored separately from posts, but you can’t use LEFT JOIN otherwise we will get a mess from a bunch of duplicate posts in the selection.
I thought about the option to get the posts, and then collect the IDs of the received posts and pull out 3 comments for each using UNION. But if there are 40-50 posts on the page. then it turns out 40-50 UNION.
What other ideas could there be?