@Robert Han- We followed this sample (https://github.com/OfficeDev/Microsoft-Teams-Samples/tree/main/samples/graph-activity-feed/nodejs) and were able to get activity feed notification in both MS Teams Desktop, Web and mobile client.
*MS Teams Version IOS: 6.17.77.2024173101/0919
MS Teams Version Android: 1416/1.0.0.2024162202/0827
Also check,* the app is needs to be added to a mobile whitelist.
POST https://graph.microsoft.com/v1.0/teams/xxxxb29b-2dde-4682-xxxx-4ec85e5bxxxx/sendActivityNotification
{
"topic": {
"source": "entityUrl",
"value": "https://graph.microsoft.com/v1.0/teams/xxxxb29b-2dde-4682-xxxx-4ec85e5bxxxx"
},
"activityType": "pendingFinanceApprovalRequests",
"previewText": {
"content": "Internal spending team has a pending finance approval requests"
},
"recipient": {
"@odata.type": "microsoft.graph.aadUserNotificationRecipient",
"userId": "xxxx3913-2766-4e6f-9edb-90d52bfxxxxx"
},
"templateParameters": [
{
"name": "pendingRequestCount",
"value": "5"
}
]
}