I hope whoever negotiated with GoDaddy and let them completely destroy M365 is locked away in a basement somewhere. Never to be heard from again.
We've moved a few clients from NoDaddy to clean M365 tenants many times. We usually do a PST export prior to the move and then import once finished. OK for small clients with a few mailboxes. Ideally no mailbox too large.
The best tool we have is powershell. Some notes below. They vary from time to time and every migration is different but you may pick up some tips here. Removing the domain from the GoDaddy M365 portal seems to be a lot more automated now. Notes below are a guide only.
You need to remove all instances of any user or group using the domain before you can remove it.
For large migrations, BitTitan is the preferred method.
For small migrations, you can do manually with PST export and import but new Outlook may cause a challenge.
Create a licensed account and delegate all other mailboxes giving you access in Outlook.
Export each mailbox PST to a file before the cutover.
If loss of mail is absolutely not an option. SMTP mail with a forwarder is an option but a lot of work. The client needs to be aware there may be some time when mail does not exists.
We usually do the migration on a Thursday night late with the Friday to work on any issues.
If you use Powershell
Install-Module MSOnline
Install-Module AzureAD
Import-Module AzureAD
Get-MsolUser -DomainName godaddysucksballs.com.au
Remove-MsolUser -UserPrincipalName "guyinbasement@godaddysucksballs.com.au"
Remove-MsolDomain -DomainName godaddysucksballs.com.au -Force
This should clear up this domain and allow you to add to the new domain. Can take some time but usually pretty quick. If you've set up the new tenant correctly, adding the domain and changing user names is pretty much all you need to do. Make sure the MX record is correct and update any DNS settings that may vary.
Follow up with the client is key. Being available after the change to address issues is important.