We're seeing a small, but steadily increasing, flow of problem reports, in Blogger Help Forum: Get Help with an Issue. Problems being reported look similar to those typically seen with domains purchased long ago using "Buy a domain", before the "Transition" period was introduced to Blogger custom domain publishing.
Google Domains has been in Beta status just about a month - and integrated with Blogger, for about half that.
We're seeing various problems reported, with domains using righteous DNS addressing - which look reminiscent of symptoms common to "Buy a domain", before the legendary "Transition" period was introduced.
- Blogs won't publish to a purchased domain, with mysterious error messages like "code CONFLICT".
- Blogs will publish, but show "404 Not Found" for the BlogSpot, domain root, and / or "www" alias.
- Blogs will publish, but the BlogSpot URL displays a long remembered oddity
This blog is not hosted by Blogger and has not been checked for spam, viruses and other forms of malware.
- Blogs will publish, but the domain root cannot be redirected - and again, show mysterious error messages like "code CONFLICT".
We have a new Problem Rollup topic, in Blogger Help Forum: Get Help with an Issue, where we are requesting details from everybody who is experiencing this problem.
While we wait for action by Blogger Engineering, everybody experiencing this problem is strongly urged to contribute their details to the Rollup Discussion. Problem diagnosis being as it is, any one person, contributing their details, might contribute the one essential detail that leads to successful diagnosis of the problem.
(Update 3/20): With the discovery that Google Domains offers real time, on line contact, several blog owners have contacted them. In some cases, they have suggested simply changing the target DNS address from "ghs.googlehosted.com" to "ghs.google.com"; in other cases, a more complicated remapping exercise.