dowloading git-cl, connection timed out

[pubabhervegueguen]

Hi all fellow developers,

My name is Gerard and I want to seek if I can do something about 
traditional Japanese notations.

As the subject is rare and difficult (such as vertical writing and quite 
many different notations depending on instrument schools), I do no 
expect to find a community already or wishing to work on the subject up 
now.

But I face a beginner's problem: timeout on git-cl download

I am following 2.25.7 Lilypond Contributor's guide,
I Installed the proposed Debian 11 from zip on Oracle VM Virtualbox, my 
host is Windows10 secured by default Windows Defender.

When running  ./setup.sh, I get the following error message:

Cloning into git-cl...
fatal: unable to connect to github.com:
github .com[0: 140.82.121.4]: errno=Connection timed out

I can access to the internet (via Wifi) with Firefox, for instance to 
https://github.com

In VirtualBox I tried NAT and Bridged configurations, with no success.

Can someone give me a clue to help?

Thanks in advance, cheers,
Gerard