I have found multiple sites where they are reported in webkitgtk as having TLS errors. The reported error says the certificate authority is unknown, but we do have the corresponding root certificate on the system.
You can test one these 2 sites: healio.com and onbase.com. This bug is present in the GTK Minibrowser.
Apologies. The 2 test sites should be healio.com and my.intercall.com.
This was resolved in . Turns out it was a bug in glib-networking 2.41.4.