Sidebars are a great place to show people your lead magnets. They are popular and useful for bloggers. When someone goes straight to the post on your blog, they will see your sidebars where they can opt-in.
You should use your sidebar to promote your lead magnet. This is a good strategy for bloggers, and for people who want to sell something on their blog. If someone clicks on the link, they won’t go to your homepage first, they will just see the sidebar.