Architecture Hub - Blog Sidebar
You can use custom sidebars for blog posts and blog archive pages.
Go to Liquid > Theme Options > Sidebar to enable sidebars globally.
You can also find this option in Elementor Page Settings. If you set it from there, sidebar will be enabled only for the page you're editing.
Go to Appearance > Widgets and find the related sidebar. Now you can drag and drop any pre-built widget to create your own sidebar.