Encontré un workaround que me funcionó… se los dejo para aquéllos que tienen o tuvieron el mismo problema
https://getcomposer.org/doc/articles/troubleshooting.md#operation-timed-out-ipv6-issues-
Workaround Linux:
On linux, it seems that running this command helps to make ipv4 traffic have a higher prio than ipv6, which is a better alternative than disabling ipv6 entirely:
sudo sh -c "echo 'precedence ::ffff:0:0/96 100' >> /etc/gai.conf"
Saludos!