Trouble opening ports in SQL Server 2019 Express - WMI Error [0x80071779]

Update:

Going back one version to SQL Server 2017 Express allowed me to save TCP/IP ports and IP addresses entered in SQL Server Configuration Manager.

None of these variables were saved in the registry:
HKLM\SOFTWARE\Microsoft\Microsoft SQL Server**INST**\MSSQLServer\SuperSocketNetLib\Tcp}\

In SQL Server Configuration Manager this error message only appeared when an IP section had it's "Active" state set to "no":
The specificed file is read only. [0x80071779].

For me this applies to both 2017 and 2019.

Old description:

I Have installed a local SQL Server 2019 Express (SSE 2019), that I can connect to locally with:
<computer_name>/<sql_server_name>.

I have issues trying to setup static ports to enable a remote connection.

When configuring ports in SQL Server Configuration Manager (SSCM) -> TCP/IP, upon saving I get a WMI error:
The specificed file is read only. [0x80071779].

Searching for the issue lead me to this page that shows the same error message that I get.

This page describes a workaround by changing the ports and IP settings in the registry instead. However all the sub-keys to TCP: IP1, IP2, IP3 etc. are missing for me. Could someone running a SQL server 2019 express confirm that this structure is still in use for this version of SSE?

It's strange that the WMI error points to a read only issue when I am able to change the TcpPort value in the key called Tcp with SSCM (where it's called IPALL) and by restarting the server the value in registry is updated correctly.
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So far my attempts to connect remote have failed

I have:

• Opened the standard SQL server port both in my router and my firewall
• Tried to turn off the firewall completely
• Added the keys missing and their contents in the registry based on this, but did not seem to work (SSCM didn't even read from them)
• Restarted the SQL server and it's services, SQL Server Configuration Manager application and the computer several times while trying the above
• Made sure that remote connection is on in SQL server properties (was on by default)

Some remarks about Connecting locally

Update:

When using only one instance of Sql server (and with working port management) you only need to enter the servers IP-address to initiate a connection.

Old:

While this went just fine:
<computer_name>/<sql_server_name>

I was unable to connect to the SQL server locally using 127.0.0.1 or 127.0.0.1, <port>.
What's the correct syntax for connecting to the localhost?

Some suggestions were to use a comma to separate IP and Port:
<x.x.x.x>/<SQL_server_name>, <PortNumber>

Would it work just as well using a colon?
<x.x.x.x>:<portNumber>/<SQL_server_name>

Uninstalled Sql server completely and installed a one version older sql server. Setting it up the same way and the issue was solved. Updated the question as well.