This should now be working as intended. Apologies.

Arvinhadji

I just got them for free without doing any challenges. Is this normal?

Yes, if you log into the game throughout the duration of this weekend - those rewards will automatically unlock.

STOP_NOTICING_THINGS

Leia's Princess skin is the only one I missed (was out of country), and it appeared as the background of the challenges screen. I was stoked and thought it returned, but I see no way of acquiring it. Is it not coming back this weekend? If not, could you please just add it to the event in a hot-patch? I was really hoping it would be brought back, and now it's not even on Leia's skin list.

This was not a part of the Summer Community Quests and as a result likely will not be making a return this weekend. I will forward the sentiment through however.