[Win10 Desktop] No audio only in some programs and only on 3.5mm jacks/"Speakers device" (after update?)

Originally posted to r/techsupport and later to r/pcgamingtechsupport, hoping to get some insight into the potential Windows-internal side here.

Starting this weekend some programs fail to output any sound to my speakers. Primarily observed in Guild Wars 2 running in Windowed mode, also Starcraft 2 running fullscreen and its editor which is again windowed. Others such as firefox, VLC and many installer-free executables such as RPGM-based games still work. All mentioned programs including the now mute ones worked with full audio for about a month since initial installation.

The speakers are plugged into the standard MB "line out" (yes, double-checked and it works for FF+VLC) in the back. The front 3.5mm connector in the PC case is assigned to the same "device" in Windows 10 and headphones plugged in there also do not output any sound from the affected programs.

I also have a wireless headset which I had not used with this Windows installation prior to the issues appearing. Plugged in the wireless dongle, waited for generic driver install (no manual installation or third-party software prompts) and it worked just fine for the affected programs. Unlike the case front jack this appears as a separate "device" in Windows sound UIs though. To any GW2 players reading this: yes I had to switch the active audio device in-game (or set it to Default after enabling the headset in Windows), changing the in-game setting to my speakers does not fix anything.

Now for the "update" part, and where something must have gone wrong: over the weekend I manually installed updated audio drivers ("Realtek_HD_Universal_Drivers_6.0.8765.1" downloaded via MSI Live Update 6) and Windows 10, being the piece of junk that it is, installed its own updates without notifying me. Unfortunately I cannot give a proper timeline unless you can point me to the relevant system logs, I only became aware of the Win10 updates when I went to manually reboot after installing the drivers. The updates listed in the Control Panel for that date are KB4512509, KB4509094, KB4230204 and KB4463318. For some reason older updates aren't listed.

I did not get any BSODs, obvious audio glitches or warning messages. It is still possible any of the background audio services might have crashed at some point as I was not continuously playing audio. I have uninstalled and reinstalled the Realtek Audio Drivers today to no avail, unfortunately I do not have access to the installer for the previous version (no idea where MSI LU gets them).

My best guess is that a setting related to "exclusive access" or "gaming HD audio" got corrupted and is not purged by the driver uninstall. Guild Wars 2 has this feature where it automatically mutes itself when you tab out (or lose window focus) so maybe it got caught in the "muted" state and that was saved to the audio "device" settings? Can the still-functioning programs run on some generic Windows audio driver while AAA games require a dedicated library (which could then be missing/corrupt)? Unlike the fairly obvious case of graphics drivers I do not think I'd be able to notice if firefox/VLC output "low-quality" audio as long as it's above mp3 player quality.

Any pointers on what is going on and how to fix it? The Windows troubleshooting only claims "audio enhancements" don't load which does not help and for some reason opens the Control Panel window for Sound despite there being no "enhancements" options. Thanks in advance!