Audio hardware problem with certificed device: Dell Precision 3540

I'm running following laptop:

Manufacturer: Dell Inc.
Product Name: Precision 3540
Firmware Version: 1.23.0
Board Vendor: Dell Inc.
Board Name: 0M14W7

with Ubuntu 20.04.6 LTS and there seems to be hardware problem with the integrated audio. Steps to reproduce:

1. Connect 4K monitor to the single USB-C connector on the laptop using an adapter cable. (I have no-name adapter USB-C to DisplayPort adapter which doesn't show even in lshw output so I assume that's pretty simple.)

2. While monitor is connected to the system, put the system to sleep (S3).

3. Wait a bit and wake up the system.

4. Try to play some audio using the built-in speakers: audio plays fine.

5. Connect 3.5 mm headset (I used Bose QC-25 but I would assume this doesn't matter)

6. Try to play some audio.

Expected result:

Audio plays just fine and remembers the volume I used the last time headset was used.

Actual result:

No error messages of any kind appear but nothing can be heard in the headset. If I disconnect the 3.5 mm connector, the speakers will continue playing as expected.

In addition, the hardware implemented mic mute with Fn+F4 no longer toggles the led in the button.

Workaround:

It seems that the headset starts to work again if I now disconnect the USB-C connector, put the system to S3 sleep, wait a bit and wake it without the USB-C connector connected. After the system is again running, playing audio works, the mic mute led works again and connecting the USB-C to DisplayPort adapter makes the external display to work again.

It's still unknown if this is a problem in kernel audio device driver or BIOS problem or actual hardware design problem.

I haven't been able to test if this happens with a Thunderbird Dock, too, or if the problem is limited to USB-C to DisplayPort adapter only.

The monitor connected to DisplayPort is LG 43UD79-B which does contain speakers, in case it makes a difference.

Additional info:

If 3.5 mm connector is attached while the laptop is booted and external display is not attached to USB-C port, the plug in 3.5 mm port is ignored and all audio goes to the speakers by default. Getting audio to headphones requires disconnecting and re-connecting the 3.5 mm connector while the system is running.

Is this a know issue? Is there some way to avoid this problem except the workaround I found out which requires suspending the system and disconnecting and connecting cables which is cumbersome?