Caching old messages in mobile App? (like slack, whatsapp etc...)
When starting the iOS App 2.0, the app is syncing its data. This usually takes quite a while. Another thing is, that when the device is "offline" (e.g. flightmode), I'm not able to read my already received messages on my mobile app. When Offline and the app gets started, It looks like there is no time out set, when no internet connection (circle keeps spinning since minutes). Could you cache the the data and just sync "new" messages? I just checked slack app and they offer this, which is quite helpful.
This feature is complete in the native apps and cache can be reset via Settings > Advanced Settings
An offline version to be synced when online is urgently needed, particularly during long international flight, and for archiving.
Dawn Break commented
General improvements to the mobile app are needed. I've been using the Mattermost mobile app on Android for less than a month, and it's already consumed more than 1 GB of data because it loads all the resources every time (which includes GIFs/images). It's the app I have that uses the most mobile data, even more than my browser and other media/news reading apps.