It still fails with all of my extensions disabled (wipr, privacy redirect). I just get a download dialog. I don't know what the HTTP status code is, however.
I found a flagged HN submission about it and it has just about the same result for me and for others. My first tap failed in a weird way (showed some text then redirected quickly to its git repo) and all subsequent taps trigger a download.
It flashes some text briefly then gives me an 418 TEAPOT response. I wonder if it's because I'm on Linux?
EDIT: Begrudgingly checked Chrome, and it loads. I guess it doesn't like Firefox?