Other possibility would be to block the 2.1 bluetooth module from terminal using rfkill and some syntax.

Or you could use the system default way of doing it. Create a file in the /etc/modprobe.d/ directory blacklisting the module to prevent it from even loading. No loading of the module no hardware in use to create any possibility of conflict. An example from the only file I found put on the system by the people at Debian.

root@9600k:~# cat /etc/modprobe.d/intel-microcode-blacklist.conf 
# The microcode module attempts to apply a microcode update when
# it autoloads.  This is not always safe, so we block it by default.
blacklist microcode

Atheros AR9462 AR5B22 Mini PCI-E 802.11N WIFI WLAN CARD Bluetooth 4.0 2.4

Did some searching and end of that article it looks like the adapters that are compatible
can be chosen from blueman app. So, I guess it should be ok to get the Atheros with bluetooth 4.0.
Maybe better for music streaming than 2.1 that is inside the computer.

Other possibility would be to block the 2.1 bluetooth module from terminal using rfkill and some syntax.

I will order the Atheros and update here the results. 😎

The laptop has deticated bluetooth module at not so nice place to remove..

What do you think what kind of problems would double bluetooth cause? Or do I just have to try find a card
without bluetooth or remove the deticated bluetooth module first?

I have not yet tried if the old bluetooth module works or not, but maybe try it inside few days.

It would be nice to update the bluetooth with the card also to try to get ldac/aptx support..

Any toughts? Does anyone have same situation with their laptops?

I would assume it is not very easy to get the oem bluetooth module to work with linux, but will try to install the needed
software in few days and see if it is recoqnized.