KIO Client not recognising root CA-Certificate

I have a self-generated SSL root-CA-Certificate in

/usr/local/share/ca-certificates/skynet.crt

The file is in PEM-format.

After I copied skynet.crt into /usr/local/share/ca-certificates, I ran

sudo update-ca-certificates

Now I also added the certificate to the firefox root-certificates, and to the chrome root certificates.

I can run a website on https://localhost:5007 with a SSL certificate issued by this authority (skynet.crt).

It works fine on Firefox and on Chrome, if I run the website first, then start chrome/firefox, and enter https://localhost:5007 in the address bar.

But when I run the website from JetBrains Rider, and it opens the website (in Firefox) at https://locahost:5007, I get an error in KIO Client:

i click on details, and I get

I close the error details, and click continue, I get this screen:

Since I don't want any permanent entries, I click "Current session only"

the it opens chrome, and I get "secure connection failed".

Now of course I get this error, because the skynet certificate is already in the firefox store.

But why does the KIO-Client recognize this as invalid certificate ?

Does it use its own certificate store ? Or do I need to do something more than update-ca-certificates, until the certificate is accepted ?

Or what's the problem ?

Note: I can reproduce the problem, if I execute:

kioclient5 exec https://localhost:5007

This seems to be an issue with the version of firefox in the ubuntu repositories.

To fix the problem:

• Install firefox developer edition.

• Make a backup of /usr/share/applications/firefox.desktop.

• Remove and purge the system firefox.

• Copy the backup to /usr/share/applications/firefox.desktop

• Create /usr/bin/firefox with content

  #!/bin/bash

  exec -a "$0" "/opt/mozilla/firefox/firefox" "$@"

where /opt/mozilla/firefox is where you installed firefox developer edition.

chmod +x /usr/bin/firefox

Done.

You can now start it with

kioclient5 exec https://localhost:5007

and it just works.