jekyll
Use site or page language
Rather than hard-code to use en-US, pick up the language tag from the page or site in the same way as the minima layout.
Hello @me-and, this HTML page is actually the layout for generated redirect pages. Therefore, page.lang will always be undefined or null leading to unnecessary calls to the Liquid filter default. A better solution would be adding this attribute directly to the generated Redirect page via Ruby.
I recommend testing above hypothesis and solution using a sample site and make the necessary changes here.
I had the impression that one could set page.lang in the same place as page.redirect.to, but I was just trying to get a quick fix when I spotted a redirect I'd created using GitHub Pages unexpectedly giving en-US as the language, so I could well be misunderstanding how these things fit together!
In any case, I'm not sufficiently invested to set up a test environment, so if this isn't a quick and helpful fix and nobody else wants to fix things properly, I'm happy to just drop it.
Unfortunately yes, you have misunderstood the markup here. The generated redirect page(s) simply render an unstyled Redirecting... which is in en-US locale (or en lang).
So, if we were to interpolate page.lang to be say, fr_CA but still continue rendering Redirecting..., now that would be a bug / incorrect render.