For topics related to the XZ projects, including security issues, the address is xz at tukaani dot org. The XZ projects also have mailing lists.
For other questions, Lasse Collin’s email address is lasse dot collin at tukaani dot org. Sometimes I’m a bit slow to answer. If you don’t get a reply within two weeks, assume that the email has got lost and try either resending or use the other contact methods below.
If needed, Lasse’s OpenPGP key fingerprint is 3690 C240 CE51 B467 0D30 AD1C 38EE 757D 6918 4620.
The XZ projects repositories are on GitHub under the Tukaani organization.
The Tukaani project’s IRC channel is #tukaani on Libera Chat. The channel is usually quiet so just ask your question and someone might wake up.
The IRC nicks of the project members:
Larhzu: Lasse Collin
jiatan: Jia Tan
A handful of friendly community members are regularly online too.
Remember that people are from different timezones and not online every day. If you get no reply and cannot leave your IRC client online, try the other contact methods listed above.