Please update your Mattermost version, your version is no longer supported by the Mattermost Android app.
Bring your Mattermost version up to date so that all features work on the Mattermost Android app and the app stops throwing a warning that the server version is out of date and not supported.
Kristijan Knezevic commented
I do agree with this request.
The current latest version on the extensions tab is 5.26.5-1 while Mattermost is on version 6.
Version 6 of Mattermost brings a lot of features and fixes that are a must have.
Please, please update Mattermost to version 6.