I met the same issue on android mobile 2.1.0 (Build 2000461) with Server Version 7.9.1.
The mobile app will offline quickly even I added it to disabled power saving list.
I’m not sure what’s the problem and I checked mobile app changelog, Mattermost mobile apps changelog — Mattermost documentation, I see the item “Added support for changing the mobile client status to offline when the app loses connection.” in 1.15 mobile release" . so I’m wondering it might be the issue that a mobile app lost connection?
For now I already disable power saving option, the status still change to offline after I switch to another android application and I’m pretty sure the mattermost application doesn’t hibernate.
We need team member show status online when his mobile application is opened , so this is the case really anonying.