Currently there is just the dhcpcd-discuss mailing list, which is powered by mlmmj. One interacts with mlmmj via email.
To subscribe to the list, send an empty email to firstname.lastname@example.org.
Once subscribed to the list, you can post to it by sending an email to email@example.com.
To unsubscribe from the list, send an empty email to firstname.lastname@example.org.
You can learn more about the capabilities of mlmmj by sending an empty mail to email@example.com.
You can also read the dhcpcd-discuss archive.