As they have not been mentioned before: We played „The Witness” and “Return of the Obra Dinn” together and are currently solving “The Case of the Golden Idol”

Not true in all cases. Due to how the web security model works, unlike a native app, a web app running on wefwef.app cannot randomly access other domains. This includes contacting lemmy instances. This is the reason why they implement a proxy (see code here). From what I understand newer lemmy server versions do (or will soon) implement CORS which is a mechanism that obsoletes the requirement for a proxy and allows direct communication between web app and instance.