Keyboard users will get a "Skip to main content" link when using a Canvas app in a browser. The problem is that selecting this link doesn't do anything. To meet WCAG 2.4.1 Bypass Blocks, selecting this link should change the user's focus to the main part of the app.
The fix would be to let the developer set the element target of the "Skip to main content" that should be focused. Right now it's just confusing to screen reader users because it doesn't do anything.