I also noticed on my work machine (Windows 11, Edge) the event stream doesn’t work. On my MacOS and iOS systems there is no problem, so I didn’t check further. The error I see saw in the log was similar to the one described here: Testing Service Workers locally with self signed certificates
“Failed to register ServiceWorker … SSL certificate error”. I can check the other day when required.
My OpenHAB installation has a self-signed certificate and I didn’t bother to import it as trusted so far.