Multihost from which one is WordPress – Pointing URL to a directory

Hi all,

I’m a novice at WP but working with it, I’m starting loving it, so thank you the whole WP community for this lovely tool/piece of software.

Now, I bought an NAS which has many packages through which WordPress as well. This NAS listens on port 80 for http management, however, I changed that to a different/custom port and then enforced redirection to https so that entire NAS is manageable from inside only (behind the firewall). Now, on the firewall I opened an Access Rule for port 80 on the Public IP and created the necessary Inbound Nat Policy. However, when trying to access from outside via the Public IP via http which is forwarded to the internal IP of the NAS, I get the redirection to https for https management authentication of NAS, instead of getting the WordPress page.
On my registered domain, the A DNS record obviously can point to my public IP only – not the entire path to WordPress.

Current configuration:
https://PublicIP/adv,/pkg/WordPress –> works fine

Desired config:
https://www.domain.com –> to take me to the WordPress main home page

The DNS A record translated the https://www.domain.com to PublicIP only.
Which means it would work only when:
https://PublicIP –> would take you to WordPress Site Main home page.

Going into the WP configuration under Settings>General Settings there are two entries:
WordPress Address: (Url) https://InternalIPNAS/adv,/pkg/WordPress
Site Address: (URL) https://internIPNAS/adv,/pkg/WordPress

I suppose if adjusting the later Site Address to https://domain.com would sort the issue? How do you do that, since is grayed out and cannot change it at all. How do you guys modify that?

If anyone has faced this in the past, any help or ideas are appreciated.

Thank you all,
Kind regards, byStancouk.