The current pre-release of the client ("pioneer" in the version) is only compatible to itself. So you can only play with other testers. Please be aware!
If you want it for yourself, go for it. But for others it's always easy to figure out who plays/played via client, ice adapter debug view or replay information
@amygdala That is very interesting because I had disabled all notifications. Unchecking the box for the "After game review" notification in the notification settings in FAF did resolve this issue though.
Thank you for your help.