linode install of mastadon via Cloudron

[DeBossNow]

1. set up linode account
2. Cloudron first app install (in order to install Mastadon)
3. Forwarded a test domain of mine from GoDaddy to Linode
4. mytestdomain.com (fake name) now replaces the assigned IP 129.blah blah of my Linode Ubuntu server instance
5. Used Cloudron to install Mastadon
6. made username for my admin dashboard
7. Installed RoundCube and successfully can send email from another email host I have to (fake names) myadminname@mytestdomain.com

Now I want to, via one method or the other, to apply a new domain name to my Matadon application.
As in: https://mynewdomain.com in a browser will open immediately to my Mastadon server installation -- to the Public Users generic page with info about signing up, etc.

From what I have read once Mastadon is setup (like mine) to use one domain then I can't simply go through steps to change my default domain url to a new domain.

To install a Mastadon application using another URL than the one now installed where do I begin?

because the linode dashboard is now using my previous domain url do I have to set up ANOTHER Ubuntu installation and assign the new URL intended to be used by my Mastadon application?

Or do I have to set up a completely new Linode account for exclusive use of my new URL so that I can use a New Cloudron installation and then another installation of Mastadon?

Bouncing back and forth beween Linode, Cloudron and Mastadon documents I can't see the Best Use solution.

Thank you for answering with the Steps I need to implement!

[robi]

@debossnow In Cloudron you can easily change the domain of any app by using the gear icon and the location section menu.