EXPECTED RESULT
Before, when I connected Bluetooth earphones, Plasma's sound settings would only show the speaker of the earphones connected as A2DP something.

Then, if I went to Google Meet or some other website that needs the microphone, it would switch to the "Headset Head Unit" mode and a microphone option would appear in the settings. I could either select the microphone in the website/app, or keep it Default/System there and change the system default from Plasma settings.

This would then be remembered. If I closed the website, the earphones would switch back to the A2DP thing with no microphone. But then if I reopened Google Meet, Plasma's default microphone would change to the earphone microphone automatically.

OBSERVED RESULT
Currently, Plasma's sound settings always show the earphone microphone, even when the earphone is in the A2DP mode. But if I switch to it as the default and open Google Meet and select the system default mic there, other people can't hear me.

Regardless of whether I change the microphone defaults from Plasma settings, it never switches to the Headset Head Unit mode automatically any more. I now have to select the earphone microphone from the website manually, and only then a duplicate of the microphone would appear in Plasma settings, and all three (speakers + two microphone copies) would switch to the Headset Head Unit profile.

But even if I select this new copy of the microphone as the default in Plasma while Google Meet is opened, since the profile switch no longer happens automatically, it isn't automatically selected the next time. I would have to select the earphone microphone manually again on the website, which would cause the profile switch. But then I can immediately go back to the Default/System microphone on the website because now with the switched profile, Plasma remembers the default microphone change.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 6.10.10-200.fc40.x86_64
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.6.0
Qt Version: 6.7.2

ADDITIONAL INFORMATION
This actually started happening a few months ago. Back then, I thought the earphone microphone was completely broken, so I just started using the laptop microphone, hoping that it would be fixed in some future update. But only recently I realised that it is a bug with the profile switching mechanism.