Is there any dedicated, academic channel i could use to establish contact with other universities on an international scale?
Summarizing the comments: the primary form of communication and dissemination of information among academics is e-mail, for better or worse.  But perhaps more towards what your end goal might be, a Slack channel might be appropriate.  You will still need to solicit participants via e-mail and advertising on ResearchGate or listservs dedicated to your research field.  But once you get a core group, you can put everyone on Slack and give them admin permissions to add additional participants as the group grows.