Well, with my limited experience in v11 this is what has worked for me:
(This is for changing the name of a site)
Goto the /sites/site1.local and edit the site_config.json and delete all entries EXCEPT the database name and the database password lines. When done is should look something like this:
{
"db_name": "1bd3e0294da19198",
"db_password": "Ys18oHjmt4kOJklP"
}
(Make sure there is no comma after the db_password)
Save the file and then run:
bench setup nginx
sudo service nginx restart
At this point any URL associated with “site1.local” site has been removed, and any attempt to access the site will result in the “Sorry, try again later” message in the browser. However, the system is now ready to assign a new name. So run the following commands from ~/frape-bench (replace new.sitename.net with your new URL)
bench config dns_multitenant on
bench setup add-domain --site site1.local new.sitename.net
bench setup nginx
sudo service nginx restart
At this point you should be able to access the site through the browser with your new URL although it will not be secure until you also run the lets-encrypt command to generate a certificate.
I do this alot with v10 and have already done it once with v11 and had good success as long as there is nothing else wrong with the underlying system. But as I have discovered from another installation issue, not everyones system works the same.
Your Mileage May Vary… 
Hope this helps.
BKM