No worries, I'm happy to hear back.
@max no it hasn't. I haven't tried in a while though (since june), the computer is at the lab and I cannot access it myself. I'll retry as soon as I can.
@giuliomoro thanks for the information on the drivers. I'm wondering could reinstalling them be of any use? As in the Windows transition would have maybe messed something up and it just needs to be reinstalled properly? I haven't had the occasion to try this yet.
Any idea on other potential underlying reason for such issue? Another guess was weirdyness of the port communication protocol (I mean TCP, UDP, or which ever is used) in Windows 11, but I'm not knowledgeable on the matter. However if it was about this, I would expect more people to encounter the same problem transitionning to Windows 11. But we have another work for which we use TCP communication with a local server and it started to display very weird exessive delays around the same period the problem with Bela IDE occured. We don't know if delays come from the communication with the server but it is a possibility.
An important precision I forgot to mention in my original message is that, although the IDE doesn't load, the board is recognised by the computer and mounted properly. We just can't access it via the browser IDE. We are (and always have been) using Firefox to do so. But to be sure I tried on Edge and Chrome. Didn't work either.