Use this template for drop-in replacement from the jekyll-redirect-from style of creating redirect files from old routes to the route of the current page.
In the front matter or data of a page, add one or many redirects:
Single
redirect_from: /old-url/page
Multiple
redirect_from: [/old-url/page, /some-other-page]
Does this still work for you on Eleventy 2.x?
I think during some update this broke for me, still trying to figure out what happened