Comment # 3 on bug 1128358 from Gerben Venekamp

Observation: starting the Slack flatpak during KDE Plasma startup seems to
result in no network connection quite often. Staring it later by hand there
seems to be no connection issues. Starting Slack automatically is done by its
provided .desktop file.

Of course during KDE Plasma start up, the network must be configured by
Networkmanager. An initial no network connection is expected. However, quitting
Slack and starting it after the network has come on line, Slack or any other
flatpak app will not have a network connection at all. The observation here is
that it seems one should not start any flatpak app before the network is fully
initialized. Once initialized, moving across networks (home, office) does not
seem to cause for issues.