Your query is a bit unusual, so let’s try to elaborate a bit what it is you’re after. 443 usually isn’t a problem as it’s used for secure web traffic (HTTPS). If you are behind a router (as most are, since modems usually route), the router probably has that open and answers knock on that door and can either forward it directly (default) or via port forwarding send it to any other port. I’m not sure, but inability to have that secure traffic reach your web browser via 443 isn’t automatically re-routed and you’d need to set up an alternative. Or face that you wouldn’t browse, since many sites use HTTPS (an alternative, if you have your desktop for other things only).
And just to be clear, a closed port needs to be clarified as well: the port is closed, when an app/service is not listening to it. Disabling a port on the other hand is usually done at firewall (with various filters of what kind of traffic and to which direction). If it’s not answering anything to packets, it’s directing things to /dev/null (“the void”, deny traffic as there is no reply, it’s the so called “stealth mode”- marketing speak for W users).
So, please provide more info and perhaps rephrase what your looking for. It may be relevant to understand why you’d want to cease secure HTTPS. For straight up firewall commands to set up dropping incoming to a port, search for ufw (or its graphical user interface gufw) and how to set up rules.
Some previous PureOs firewall threads:
Limiting Internet access in an app-by-app basis on PureOS?,
How to setup GUFW firewall?,
How do I get ufw firewall to enable by default?.