I don't see this catching on any more than humans.txt did, tbh. The spec has some issues anyway: requiring .txt even though it's markdown, and requiring a particular URL structure for no good reason instead of leveraging <link rel="alternate">, which is already an existing web standard (i.e. there's no need for this spec in the first place). Putting the file in the site root instead of .well-known doesn't help, either; humans.txt did the same, but only because it was a play on robots.txt. It's not 2011 anymore.
I don't see this catching on any more than humans.txt did, tbh. The spec has some issues anyway: requiring .txt even though it's markdown, and requiring a particular URL structure for no good reason instead of leveraging <link rel="alternate">, which is already an existing web standard (i.e. there's no need for this spec in the first place). Putting the file in the site root instead of .well-known doesn't help, either; humans.txt did the same, but only because it was a play on robots.txt. It's not 2011 anymore.