How do I remove another user from an alert?

Do you have permissions to edit alerts? Should be as easy as navigating to the card, either on the card/DataSet or Alerts in the top nav bar, then clicking share on the bottom of the alert, then expanding the already shared with section, then clicking the x on the far right on their name.

If you are talking automation, you can use the Product APIs for that. Authentication documentation: developer.domo.com/portal/8ba9aedad3679-ap-is#product-apis.

POST https://<instance>.domo.com/api/search/v1/query

Body:

{

    "count": 1000,

    "offset": 0,

    "combineResults": false,

    "query": "*",

    "filters": [

        {

            "name": "OWNED_BY_ID",

            "field": "owned_by_id",

            "facetType": "user",

            "value": "<user_id>:USER",

            "filterType": "term",
            "displayValue": "<user_name>",

            "translatedDisplayValue": "Owned by: <user_name>",

            "translatedPlaceHolderText": "Search people"

        }

    ],

    "sort": {

        "isRelevance": true

    },

    "facetValuesToInclude": [

        "TYPE"

    ],

    "facetValueLimit": 0,

    "facetValueOffset": 0,

    "includePhonetic": true,

    "queryProfile": "GLOBAL",

    "state": "list",

    "topic": null,

    "savedSearchId": null,

    "entityList": [

        [

            "alert"

        ]

    ]

}

Then loop through those results:
DELETE https://<instance>.domo.com/api/social/v4/alerts/<alert_id>/subscriptions?subscriberId=<user_id>&type=USER