Custom tab app cannot be added to a shared channel

Question

I'm trying to add a custom tab app in a shared channel. However, when doing so it is saying that it isn't supported in shared channels.

The manifest.json is as below

{
    "$schema": "https://developer.microsoft.com/en-us/json-schemas/teams/v1.19/MicrosoftTeams.schema.json",
    "manifestVersion": "1.19",
    "version": "1.0.0",
    "id": "${{TEAMS_APP_ID}}",
    "developer": {
        "name": "Teams App, Inc.",
        "websiteUrl": "https://www.example.com",
        "privacyUrl": "https://www.example.com/privacy",
        "termsOfUseUrl": "https://www.example.com/termsofuse"
    },
    "icons": {
        "color": "color.png",
        "outline": "outline.png"
    },
    "name": {
        "short": "simple-tab ${{APP_NAME_SUFFIX}}",
        "full": "Full name for simple-tab"
    },
    "description": {
        "short": "Short description of simple-tab",
        "full": "Full description of simple-tab"
    },
    "accentColor": "#FFFFFF",
    "bots": [],
    "composeExtensions": [],
    "staticTabs": [
        {
            "entityId": "index0",
            "name": "Home",
            "contentUrl": "${{TAB_ENDPOINT}}/tab",
            "websiteUrl": "${{TAB_ENDPOINT}}/tab",
            "scopes": [
                "personal",
                "groupChat",
                "team"
            ],
            "context": [
                "personalTab",
                "channelTab",
                "privateChatTab"
            ]
        }
    ],
    "permissions": [
        "identity",
        "messageTeamMembers"
    ],
    "validDomains": [
        "${{TAB_DOMAIN}}"
    ],
    "supportedChannelTypes": [
        "privateChannels",
        "sharedChannels"
    ]
}

Is there anything that I've missed? The documentation suggests that tabs are supported in shared channels. Note that this is in debug mode and not yet published to the organization. Thanks for your assistance.

Answer 1

Update: I've published the app to the organisation so now it appears in "Built for your org" page. When I try to add the app and I search for the channel that I want to add it to it is not showing (only standard channels appear on the list:

When I search for my shared channel, it says that app isn't supported in shared channels: