For an optimal user experience, we strongly recommend upgrading both your Mattermost Desktop and Mobile Apps to the latest version. The latest versions include the latest security fixes, and are compatible with the oldest supported extended support release of Mattermost Server to ensure backwards compatibility.
Please review the Desktop App changelog and the Mobile App changelog notes for any self-hosted or Cloud-specific version requirements for features and functionalities, as well as notes on security fixes.
Upgrading Mattermost Desktop and Mobile Apps to the latest version is not mandatory when upgrading to Mattermost Server v6.0. Earlier 4.x versions of Mattermost Desktop App, and earlier v1.x versions of the Mobile App, will continue to be supported with a Mattermost v6.0 Server.