RSS broken?
From a Fediverse reply:
Looks like the link for this in the RSS feed is broken. This is what got delivered to my client:
/typelevel.github.com/blog/2023/04/03/typelevel_toolkit.html
It looks fine in Firefox Livemarks, but it fails W3C validation.
Thanks for opening this for me, Ross!
I realize now my post on the fediverse might make it sound like I just got the URL and not the post. I did get the full post as expected (delivered to the Reeder app via Feedbin), but trying to follow the link 404s. This is true even if I copy-paste the link from the feed XML into a browser and add https:/ manually.

I think the issue is the domain name. The error suggests changing from typelevel.github.com to typelevel.github.io, which does take me to the right page (redirected to typelevel.org). So perhaps the right fix is updating a base domain somewhere to either the github.io subdomain or typelevel.org?
Just noticed this issue too when scalanews.net tries to generate articles using rss. I manually had to add the base url of https://typelevel.org.