I cannot see that route in the OpenAPI spec here https://esi.evetech.net/latest/swagger.json
That would explain the 404 response.
ESI issues go here Issues · esi/esi-issues · GitHub and SSO issues go here Issues · ccpgames/sso-issues · GitHub but generally it seems to be a waste of time using the Github issue trackers for Eve. It’s more of a PR landing page to tick off the “We’re opensource” checkbox.
Also don’t hope for a notice about upcoming changes on any public API from CCP, they even broke their own example code when they pushed out a “non breaking” change to their JWT and broke everybody elses code too in the process.
If you want an alert on API changes you can simply run a diff locally of the OpenAPI spec or compare against a stored hash of the previous check and schedule it daily push out a notification.