flatpak run com.skype.Client
results in
SIGABRT

First I installed Skype system wide, removed it and then installed it again as a regular user, both with the same result.

What should I do to resolve this issue?

You can install in Discover, probably you change some env variable.

Can you try with running export $(dbus-launch) first, then start Skype. Nothing special should be needed, can be run that way system wide.

3 months later

plaken I have the same issue

Not the same issue, there is no need to run dbus-launch anymore for Skype, Slack has entire different issues.
Closing this old thread (please take the advice when posting in old threads presented to you).