No schema completions for `tsconfig.json`

[btalb]

I've been trying to get completions for tsconfig.json working, and have debugged as far as I can.

The README suggests that with default settings I should get support for all the schemas listed at https://raw.githubusercontent.com/SchemaStore/schemastore/master/src/api/json/catalog.json.

But when debugging with json.trace.server: "verbose" I see this:

[Trace - 7:07:56 pm] Sending notification 'json/schemaAssociations'.
Params: [
    [
        {
            "fileMatch": [
                "coc-settings.json"
            ],
            "uri": "vscode://settings"
        },
        {
            "fileMatch": [
                "package.json"
            ],
            "uri": "vscode://schemas/vscode-extensions"
        },
        {
            "fileMatch": [
                "/*.html-data.json"
            ],
            "uri": "https://raw.githubusercontent.com/microsoft/vscode-html-languageservice/master/docs/customData.schema.json"
        },
        {
            "fileMatch": [
                "/package.json"
            ],
            "uri": "file:///home/ben/.config/coc/extensions/node_modules/coc-html/schemas/package.schema.json"
        },
        {
            "fileMatch": [
                "/.prettierrc"
            ],
            "uri": "http://json.schemastore.org/prettierrc"
        },
        {
            "fileMatch": [
                "/.prettierrc.json"
            ],
            "uri": "http://json.schemastore.org/prettierrc"
        },
        {
            "fileMatch": [
                "/package.json"
            ],
            "uri": "file:///home/ben/.config/coc/extensions/node_modules/coc-prettier/package-json-schema.json"
        },
        {
            "fileMatch": [
                "/pyrightconfig.json"
            ],
            "uri": "file:///home/ben/.config/coc/extensions/node_modules/coc-pyright/schemas/pyrightconfig.schema.json"
        }
    ]
]

Seems to suggest they're either not being used or overridden somewhere.

How can I debug where these settings are coming from?