[Nextcloudpi] Correct way to switch domain?

I have NCP installed on my ODroid HC2 and been testing it for over a month now. I have registered a DynDNS domain and can access my NCP without any issues. As I want to go now in the “productive use phase” I have cnamed my domain “cloud.domain.tld” to redirect to my DynDNS domain. That done I can access the odroid but get a warning that the SSL certificate is connected to my DynDNS only. This is my first issue.

The second issue is, that Nextcloud does not consider the new domain as a trustworhty domain.

Please let me add, that my domain cloud.domain.tld already has a third party SSL certificate from my provider!

My question now is, what would be correct approach here on NCP?

I guess, setting up a new letsencrypt SSL certificate via NCP webUI should solve both issues, but how will NCP react, with 2 different SSL certificates pointing to that domain?

Did you put your new domain into the trusted_domains array in your config file?