As an update, I found this post solved the issue https://forum.cloudron.io/topic/1819/wordpress-unmanaged-re-directions-unable-to-install/4
I have example.com for the primary domain & my.example.com for Cloudron admin.
For the Ghost app, it is ghostexample.com. At first visit, it showed me the Cloudron login page. This was fixed after a while. The www.ghostexample.com going to admin page was fixed by removing CNAME & adding redirect.
Thanks for the support!