So just to finish this off and update you all, definitely for those who encounter the same problem, and also for posterity…
TL;DR
After looking into this problem further based on the fact, that swapping hardware did not really change the situation, I ultimately established couple of weeks later, that the issue I’ve encountered sits with Windows and its Bluetooth stack (audio streaming part really) which must have got damaged by couple of unsuccessful monthly CUs that I’ve also had bumped into in previous months/years.
Ultimate repair install (so-called: In-place Upgrade, so re-installation of the OS without having to reinstall anything else, settings intact etc.) has fixed this problem and all is now well.
Details
I was understandably a bit gobsmacked with all the above to date.
To re-cap: OS restore to the date/time when Bluetooth audio streaming was fully operational – so couple of weeks prior – as well as hardware upgrade (adapter migration, from AC3165 to AX200) gave me the same results: Bluetooth itself remained operational per se, i.e. I could have paired devices, exchanged data etc., but audio streaming was stubbornly not.
I then started suspecting something unhealthy back on the software front (=device driver), related to streaming audio itself. Having a work laptop aside with similar hardware on-board (AX201), I began like-for-like comparison of what I can see in Device Manager.
I confirmed that all key components related to hardware/software installation were okay – so Intel’s drivers were definitely installed fine.
I was obviously unable to locate Bluetooth Audio devices, but I found within Other Devices section couple of them related to Bluetooth which I could not have seen on the work laptop. I started looking further and what attracted by attention were
A2DP and
AVRCP Transport components (signified by missing references to A2DP and BthHfAud drivers), clearly missing within my home PC (I used Driver View). These drivers are supplied by Microsoft and form part of OS.
Subsequently, by comparing IDs of relevant devices within Registry and some hit & miss game I was ultimately able to manually install relevant drivers for these Other Devices and get to the point, where I was able to connect successfully to the audio device – also marked as such by the audio device itself – but no audio was being heard.
That has further proved that audio streaming part of Bluetooth stack must have got somehow damaged, and also sometime earlier than late Oct. I am guessing – but only guessing – my experiences with unsuccessful monthly CU deployments as documented all here contributed to this very issue:
KB5014699 Windows 10 19042.1766, 19043.1766, 19044.1766
[SOLVED] - Windows 10 - KB5007186 (Nov CU) ends up with 0xe0000100
[SOLVED] - Windows 10 - Updates since KB4512508 (Aug CU) end up with 0xe0000100
(Please note that – interestingly – files that got knackered were actually BT-related!)
I am also guessing that damage must have occurred relatively recently – probably upon the latest occurrence, in Jun 2022, otherwise this problem would have surfaced much sooner. Also, back in Jun I actually tried to revert changes using System Restore – in vain though, should have used OS image really, as OS got stuck @ Restoring Registry stage from which I had to restart it by hard power down. Which is exactly what may have damaged these components.
So to sum up, what has taken place probably is this: the damage to Bluetooth audio streaming stack must have happened in Jun during CU unsuccessful deployment and my subsequent mop-up exercise to revert & resolve; the resulting instability was not visible & known until I possibly and very likely – my new work laptop is only few months old – tried to connect to / pair with new audio device and that has resulted in this part of OS suddenly stopping working late in Oct.
I then paused – life’s too short for any such further manual experiments at this stage – and after some thinking decided to resort to the option I really didn’t like, which was repair install, or – as it’s known – In-place Upgrade, so re-installation of the OS without having to reinstall anything else, settings intact. The other option I’ve had was to revert to Apr OS image, but then I had no guarantee that the above damage was not inflicted sooner (so would have achieved nothing and wasted another evening or so). Also, having to upgrade quite a few programs and thinking very carefully what I installed since then would also be a bit of a challenge.
And so, come one evening late Nov, and few hours later all is well and I’m sorted, and despite me having lost ca. 1 month worth of updates to OS and various other software, and having to go through re-indexing of all my contents, and other minor boring nuances as a result of this operation.
Please finally note that any usual OS repair methods: DISM or SFC are pointless and to no avail. Why is this the case? That’s possibly story for another occasion.
I hope someone will find the above useful – meanwhile will mark this thread as resolved.
I will also update other forums I sought information from (TenForums, Intel, HP) accordingly.
