I recently developed a plugin locally for Confluence. We are using Confluence Cloud. Since I can’t upload the jar file directly, I created a vendor account on the marketplace and uploaded the plugin file as a private app. However, the listing indicates that it is “for Confluence Server 6.4.2.” A Cloud version is not available.
How do I make my app available for installation on our Cloud account?
Cloud plugins are created using a completely separate API/integration points from Server plugins. You will never, ever, be able to upload jar files for Cloud.
Rather, all Cloud plugins are instead ‘plugin as a service’: They remotely request your resources, remotely send you webhooks, and you remotely interact using the REST API.
You’d have to either redevelop your plugin for Cloud OR create your plugin in such a way that you can also support Cloud Services with the same package (albeit from your own hosting provider).
Have a look at the Cloud documentation first, here - it’s a different thing: Confluence Cloud
There’s some work ahead of you - and some things just can’t be done in Cloud. And you need to host your app as a Service.