Although I don't post much there, I regularly visit the German forum.
kartonbau.de - Kartonmodellbau, Kartonmodelle, Cardmodels, Cardmodeling
Is a great site full of nice people. And some German members who are there have also come to share their works with us here.
The Spanish forum also has some very good modelers. Again, some of them also like to come here.
https://maquetasenpapel.mforos.com/
The above mentioned French forum is another one I like to visit from time to time