Summary says it all I think.
Only the server mentioned and only at home through wi-fi/fiber connection do I have this slowness. Not through 4G and never with other server (eg FramaTeam.org)
Observed behavior
Connection, message sending, updating… Everything is slow with the app. Like nearly 10 seconds to update.
No slowness through web, though.
I meant my home internet connection: optical fiber.
I couldn’t find the problem. I installed a network sniffer on the android phone (a pseudo VPN which intercepted the traffic to be send over a wireshark through SSH), and when activated, everything went fine.
In the end, I rebooted my internet box and then everything resolved. No problem anymore (so far).
I don’t understand what happened.
It could be a multitude of things, 99% of which most likely had nothing to do with Mattermost and the app itself, and more along the lines of routing conflicts, etc, within your internal home network, all of which would auto-resolve on a reboot. I’m glad to hear you got it working!