I see the xenial directory here: http://files.freeswitch.org/repo/ubuntu/freeswitch-1.6/ , but it complains of not being signed:

# curl https://files.freeswitch.org/repo/ubuntu/freeswitch-1.6/freeswitch_archive_g0.pub | apt-key add -

# echo "deb http://files.freeswitch.org/repo/ubuntu/freeswitch-1.6/ xenial main" > /etc/apt/sources.list.d/freeswitch.list

# apt-get update

Get:4 http://files.freeswitch.org/repo/ubuntu/freeswitch-1.6 xenial InRelease [3,181 B]

Ign:4 http://files.freeswitch.org/repo/ubuntu/freeswitch-1.6 xenial InRelease

[…]

W: GPG error: http://files.freeswitch.org/repo/ubuntu/freeswitch-1.6 xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1FDDF413C2B201E5

W: The repository 'http://files.freeswitch.org/repo/ubuntu/freeswitch-1.6 xenial InRelease' is not signed.

(Note: Yes I’ve been successful with Debian Jesse, not successful with CentOS 7 because of Flite and V8 issues, but now am trying in Ubuntu as well)