Changing domains is rough, and involves manual intervention. There is currently no automatic or seamless method for doing what you are trying to do. That said, you do have options:
1. You could export a site from the Tableau Server on your old domain, and import the site onto the Tableau Server on your new domain. Import or Export a Site
- This involves manually mapping usernames to usernames so content ownership stays the same.
2. Backup the Tableau Server on the old domain and Restore the backup on the new Tableau Server with --no-config. Restore from a Backup
- You would then need to add all users from the new domain, and manually change ownership of all content to them before you could delete the users from your old domain. Manage Ownership
Again, both of these involve manual intervention, time, and effort. The site export/import is probably a little cleaner. If you have a lot of content and a single site, I'd recommend the site export. If you have many sites with small amounts of content, I'd recommend the backup/restore.
If you want hands-on help with either of the above options, Tableau does have Consulting Services that can likely assist you.
And if you're interested, I did find an idea forum somewhat related to this request. Vote it up if this is something you'd be interested in seeing in the product! https://community.tableau.com/ideas/6205