Welcome to Dom617b!
At least if I've setup all the new names, redirects, and certificates. Otherwise, you're not seeing this for which I have only myself to blame. The process I think could have been simple and I'll add a few notes about where Google is tying in services.
- Go to Blogger Settings and change the name
- Disabling HTTPS first may have made things a little easier as it was initially hard to follow the redirects while that was still changing
- Change the Custom Domain to the new name
- Update DNS and with Google Domains this is at least partially integrated
- In Google Domains, verify that the "synthetic record" is registered
- OR setup DNS CNAME pointing to ghs.google.com
- Redirect old name to new and in Google Domains there is a forwarding feature
- Remove the old CNAME
- Add a forwarding entry with settings as applicable
- 301 Permanent redirect
- Redirect full path (i.e. oldsite/page.html -> newsite/page.html vs to newsite/)
- Enable HTTPS redirection
- Wait - like a day or two
- New name was resolving fine within a few minutes really
- Redirects were almost instant
- HTTPS was the slowest part
- In Blogger Settings turn on HTTPS and redirect to HTTPS if not already done
Its long past time to move on from the online handle I was using in high school so here I am Dom617b! The 617b is what I use when I can't get my own name or handle when registering for some site so that ties in to the old part, plus "617" kinda looks like "bit" in 1337 and "b" for binary, so it all comes together as a Nibble handle.