I found a community made custom policy which does what you are looking for to configure Subscription activity logs to stream to event hub. https://github.com/Azure/Community-Policy/blob/master/Policies/Monitoring/deploy-diagnostic-setting-for-activity-log-event-hub/azurepolicy.rules.json
And if you want to quickly search available policies across Microsoft Azure built-ins plus any custom created community policies from the official repos I recommend using AzAdvertizer https://www.azadvertizer.net/
{
"if": {
"allOf": [
{
"field": "type",
"equals": "Microsoft.Resources/subscriptions"
}
]
},
"then": {
"effect": "[parameters('effect')]",
"details": {
"type": "Microsoft.Insights/diagnosticSettings",
"ExistenceScope": "Subscription",
"DeploymentScope": "Subscription",
"ExistenceCondition": {
"allOf": [
{
"field": "Microsoft.Insights/diagnosticSettings/workspaceId",
"equals": "[parameters('eventHubRuleId')]"
},
{
"field": "name",
"equals": "[parameters('profileName')]"
}
]
},
"roleDefinitionIds": [
"/providers/Microsoft.Authorization/roleDefinitions/8e3af657-a8ff-443c-a75c-2fe8c4bcb635"
],
"deployment": {
"location": "eastus",
"properties": {
"mode": "incremental",
"template": {
"$schema": "https://schema.management.azure.com/schemas/2018-05-01/subscriptionDeploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"eventHubRuleId": {
"type": "String"
},
"profileName": {
"type": "String"
}
},
"variables": {},
"resources": [
{
"type": "Microsoft.Insights/diagnosticSettings",
"apiVersion": "2017-05-01-preview",
"name": "[parameters('profileName')]",
"location": "global",
"properties": {
"eventHubAuthorizationRuleId": "[parameters('eventHubRuleId')]",
"logs": [
{
"category": "Administrative",
"enabled": true
},
{
"category": "Security",
"enabled": true
},
{
"category": "ServiceHealth",
"enabled": true
},
{
"category": "Alert",
"enabled": true
},
{
"category": "Recommendation",
"enabled": true
},
{
"category": "Policy",
"enabled": true
},
{
"category": "Autoscale",
"enabled": true
},
{
"category": "ResourceHealth",
"enabled": true
}
]
}
}
]
},
"parameters": {
"eventHubRuleId": {
"value": "[parameters('eventHubRuleId')]"
},
"profileName": {
"value": "[parameters('profileName')]"
}
}
}
}
}
}
}