Thank you for the hint, @tiakeicuecus1975!
Thanks to you, I found a temporary solution till they can fix it for good. We’ll be using uBlock Origin for this. In uBlock Origin, go to the “My filters” tab and paste the following line:
||chatgpt.com^$websocket
Then, click “Apply changes” (and verify your own filters are enabled). Refresh the page, and you should no longer be seeing this error message!