I tried both the offline and online installers, neither worked.
The online installer complained about "directory existing and not being empty". It was empty at the start, but obviously not later on. The installer finished but not everything was installed.
The offline installer failed with exit code ...

Yes, I just swapped to 2020-06 and it works fine with release 4.2

I installed ESP IDF with esp-idf-tools-setup-2.3.exe
In eclipse 2020-12 I installed (Help > Add Software):

CMake Editor 1.14.0
Espressif IDF Plugins for Eclipse 1.2.3.202010091505

from
https://dl.espressif.com/dl/idf-eclipse-plugin/updates/latest/

When installing the tools I got some warnings ...

On ubuntu 20.04, git clone fails:

Cloning into 'esp'...
remote: Enumerating objects: 728, done.
remote: Counting objects: 100% (728/728), done.
remote: Compressing objects: 100% (363/363), done.
error: RPC failed; curl 56 GnuTLS recv error (-9): Error decoding the received TLS packet.
fatal: the ...

After some reading I think the ADF won't solve anything because the problem is not audio, but in the bluetooth.
The more proper question I think is:

Can the ESP-32 be a central bluetooth device?

I tried to use the example a2dp_source in the IDF to connect to a BT speaker but it won't find it.
Am I missing something or do I have to use ESP-ADF?

Any quick pointers on how to modify the A2DP-SOURCE to:
- Just connect and keep it connected
- Use I2S as input

I just built the a2dp example and flashed it into the DevKit but it finds an error and resets.

E (572) I2S: /home/joan/esp/esp-idf/components/driver/i2s.c:838 (i2s_param_config):I2S communication format invalid.
E (572) I2S: I2S param configure error

I found somewhere it's 4.2, is that right?

All the question is the header