Eu só precisava executar
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EBCF975E5BA24D5E
De acordo com o link
$ sudo wget http://master.dl.sourceforge.net/project/d-apt/files/d-apt.list -O /etc/apt/sources.list.d/d-apt.list
--2018-03-18 21:39:27-- http://master.dl.sourceforge.net/project/d-apt/files/d-apt.list
Resolving master.dl.sourceforge.net (master.dl.sourceforge.net)... 216.105.38.12
Connecting to master.dl.sourceforge.net (master.dl.sourceforge.net)|216.105.38.12|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 85 [application/octet-stream]
Saving to: ‘/etc/apt/sources.list.d/d-apt.list’
/etc/apt/sources.list.d/ 100%[==================================>] 85 --.-KB/s in 0s
2018-03-18 21:39:28 (4.05 MB/s) - ‘/etc/apt/sources.list.d/d-apt.list’ saved [85/85]
android@android:/$ sudo apt-get update && sudo apt-get -y --allow-unauthenticated install --reinstall d-apt-keyring
Hit:1 http://np.archive.ubuntu.com/ubuntu artful InRelease
Hit:2 http://np.archive.ubuntu.com/ubuntu artful-updates InRelease
Hit:3 http://np.archive.ubuntu.com/ubuntu artful-backports InRelease
Ign:4 http://dl.google.com/linux/chrome/deb stable InRelease
Get:5 http://security.ubuntu.com/ubuntu artful-security InRelease [78.6 kB]
Hit:6 http://ppa.launchpad.net/christian-boxdoerfer/fsearch-daily/ubuntu artful InRelease
Ign:7 http://download.opensuse.org/repositories/home:/manuelschneid3r/xUbuntu_17.10 InRelease
Hit:8 http://dl.google.com/linux/chrome/deb stable Release
Get:9 http://download.opensuse.org/repositories/home:/manuelschneid3r/xUbuntu_17.10 Release [1,014 B]
Get:10 http://master.dl.sourceforge.net/project/d-apt d-apt InRelease [4,878 B]
Hit:11 http://ppa.launchpad.net/haraldhv/shotcut/ubuntu artful InRelease
Err:10 http://master.dl.sourceforge.net/project/d-apt d-apt InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EBCF975E5BA24D5E
Hit:14 http://ppa.launchpad.net/kubuntu-ppa/backports/ubuntu artful InRelease
Hit:15 http://ppa.launchpad.net/libreoffice/ppa/ubuntu artful InRelease
Hit:16 http://ppa.launchpad.net/system76/pop/ubuntu artful InRelease
Reading package lists... Done
W: GPG error: http://master.dl.sourceforge.net/project/d-apt d-apt InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EBCF975E5BA24D5E
E: The repository 'http://master.dl.sourceforge.net/project/d-apt d-apt InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
Eu só precisava executar
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EBCF975E5BA24D5E