Can't disable right sidebar

Hi, I'm trying to get rid of the right sidebar. It displays the search bar and Archive widgets.

- Settings: Customize > Sidebars > all 3 options set to "Content (no sidebar)"
- Page settings: default - also tried "Content (no sidebars)", no difference. Theme doesn't seem to have the option 'full width' for pages (?)
- Widgets > Right Sidebar > deleted items. When placing a new widget here, the search bar and Archive widgets disappear.

Hope there's a way to remove the sidebar :)

Much appreciated!
Thomas