- there was no way to move the "root" domain name away from Google Workspace while the account was still in service,
- after deleting the account, any access was definitely lost (I spent a lot of time on the phone with them, but they provided no help),
- the lost domain name was never "released", it remained officially under my ownership until the very last day of its registration period, even though I had no way to act on it.
- when I called that out a bug, they firmly replied that no there was no bug...
So, the lesson is: never use a domain name important for your business as the root domain name of a Google Workspace account, unless you really are sure that you will never need to move it to another registrar nor to delete the account.
The website's homepage is deceiving. The control panel they offer is really for power users. They expose literally everything, and have APIs for most things that you'd want to automate. For people who have to manage multiple domains, it's helpful.
Again, in case most people don't know this, most hosting providers are resellers of the big companies. They all do the same thing and have access to the same stuff. The only difference is that individual company's pricing and service. Pick wisely!
Never ever use any google product if you might need to talk to a human.
Moreover the domain did not belong to my GoDaddy account (which makes sense, as I created the GW account and acquired the root domain several years before I signed up to GoDaddy). So maybe it was a hidden GoDaddy account, something like a service account for the exclusive use of GW internal tools?
My main personal domain is through freedns.afraid.org, which in turn uses registryrocket.com for the actual registrar. I'm sure there are better options as far as nameservers and registrars go, but (aside from me forgetting to renew every couple years) it's been rock solid and worth every penny of whatever pittance I ended up paying for a premium account a decade-ish ago.
And then I've got a random .is domain registered through 1984 Hosting. Still haven't figured out a use for it.