Server/DC version of Reminders app is in the Atlassian Marketplace for years. There are some differences between Cloud and Server/DC versions of the app. Some of the limitations of Cloud version are caused by limitations of Atlassian’s Forge platform and some of them are not implemented yet.
Following are main differences you should be aware of when migrating from server/DC version of this app to Cloud version.
Limitations of Cloud Version
You can't send reminders to “project roles” and direct e-mail address in cloud version of the app.
There is no “My Reminders” page for cloud version. We will add this for next version of the app.
There is no JQLs for finding issues with reminders. Currently this is not possible with Forge Platform.
Advantages of Cloud Version
You can send reminders to Slack workspaces in Cloud version. This feature is not available for Server/DC versions.