For some reason, YoastSEO set my home page to the first blog post. So the home page canonical, title, and description are set to the values of the first blog post.
And when I tried to set the home page’s title/description, I got this screen instead of the form fields to set the values of the title/description:
Check Settings > Reading. If you have a Posts/Front page page set, you’ll need to add the meta title/description on those particular pages.