1. In September, Chrome 53 was released, which enabled mandatory Certificate Transparency for Symantec certificates due to Symantec's history of incompetence. Some website operators, such as Chase, asked Symantec to submit their certificates to Certificate Transparency logs in such a way that the certificate wouldn't be trusted by Chrome, triggering the ERR_CERTIFICATE_TRANSPARENCY_REQUIRED error. This is when I wrote this blog post.
2. Last week, an internal timebomb expired in older versions of Chrome causing this error message for any website using a Symantec certificate issued since June. Basically, Chrome contains a list of Certificate Transparency logs that it trusts, and this list has a 10 week expiration date. So if Chrome was built more than 10 weeks ago, there would be no trusted Certificate Transparency logs, and therefore any certificate that was supposed to be logged (such as new Symantec certs) would be untrusted and display this error message. The Chrome team was able to fix this within 24 hours by remotely disabling CT enforcement in Chrome. (When Chrome starts up, it fetches a list of feature flags from a Chrome server using a system called Finch which is independent of the normal upgrade system.)
3. Today, the Chromium packages in several Linux distros, including Ubuntu, became 10 weeks old. For some reason, they have not picked up the Finch update, and so they are displaying this error message for all Symantec certificates issued since June. This is not confirmed yet, but the current hypothesis is that the distros have disabled Finch for privacy reasons. It will probably require a distro package upgrade to fix.