Salamualikum warahmahtullah wabarakatuh sheikh. Is it haram to talk to opposite gender on online games where they play games together and also talk about dean? I heard many trying to justify this.

Ustadh AbdulAziz al-Haqqan

Yes, stay away from this because it will lead to haram. They want to talk about the deen, direct them to the sheikhs to ask their questions, don't make this an excuse to free mix.