Using the official viewer
1) Verify that Media and Autoplay media attached to your HUD are both checked in Preferences>Sound and Media.
2) Rez a regular plywood prim.
3) Using the editor, set the media for face 4 to an external website (e.g. https://www.bbc.co.uk/news)
4) Without touching or otherwise interacting with the prim, focus your camera on face 4. After a few seconds the plywood texture should be replace by the white shared media texture, and a few seconds after that the external website should load.
5)Take the prim into your inventory and attach it to a convenient point on your HUD (e.g. ATTACH_HUD_CENTER_1)
6)Expected behaviour: same as observed in step 4 when the prim is rezzed on the ground.
7)Actual behaviour: After a few seconds the standard control bar becomes visible if the mouse pointer is floated over the shared media face, but it remains plywood until either your click the Reload button or you right click the shared media face a couple of times. Then the face turns white and the web page loads shortly afterwards.
I've verified that with both Firestorm 7.1.13 (78266) Jun 14 2025 21:43:13 (64bit / AVX2) and Alchemy Beta 7.1.9.2514 (64bit) the HUD works as expected. That is, the web page loads without my needing to click anything.
I first noticed this when working on a script that calls llRequestURL. My debug messages told me that, in the http_request event, if (method == URL_REQUEST_GRANTED) returned true, but nothing else happened until I clicked the face, at which point if (method == "GET") fired. Normally I would expect that to happen after I called llSetPrimMediaParams when (method == URL_REQUEST_GRANTED).