Impossible d'installer libpython3-dev : broken packages ubuntu 20.04

Bonjour !

En désespoir de cause, je pose ma question ici :

plieby@dsw-demo:~$ sudo apt install libpython3-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
libpython3-dev : Depends: libpython3.8-dev (>= 3.8.2-1~) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

uname gives
plieby@dsw-demo:~$ uname -a
Linux dsw-demo 5.4.0-74-generic #83-Ubuntu SMP Sat May 8 02:35:39 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

c'est une distro serveur.

J'ai tout essayé, mais franchement je donne ma langue au chat. Merci !

En fait, j'ai trouvé la solution :

voir 20.04 - Unmet dependencies. Libc6 The package system is broken - Ask Ubuntu

(c'est libc6 qui est en cause, et il y a un micmac de versions).