build: Add original content from sources.list. Me like original (he says working in a fork)

sources.list

+# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
+# newer versions of the distribution.
 deb http://archive.ubuntu.com/ubuntu/ focal main restricted
 deb-src http://archive.ubuntu.com/ubuntu/ focal main restricted
+
+## Major bug fix updates produced after the final release of the
+## distribution.
 deb http://archive.ubuntu.com/ubuntu/ focal-updates main restricted
 deb-src http://archive.ubuntu.com/ubuntu/ focal-updates main restricted
-deb http://archive.ubuntu.com/ubuntu/ focal universe multiverse
-deb-src http://archive.ubuntu.com/ubuntu/ focal universe multiverse
-deb http://archive.ubuntu.com/ubuntu/ focal-updates universe multiverse
-deb-src http://archive.ubuntu.com/ubuntu/ focal-updates universe multiverse
-deb http://archive.ubuntu.com/ubuntu/ focal-security main restricted
-deb-src http://archive.ubuntu.com/ubuntu/ focal-security main restricted
-deb http://archive.ubuntu.com/ubuntu/ focal-security universe multiverse
-deb-src http://archive.ubuntu.com/ubuntu/ focal-security universe multiverse
+
+## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
+## team. Also, please note that software in universe WILL NOT receive any
+## review or updates from the Ubuntu security team.
+deb http://archive.ubuntu.com/ubuntu/ focal universe
+deb-src http://archive.ubuntu.com/ubuntu/ focal universe
+deb http://archive.ubuntu.com/ubuntu/ focal-updates universe
+deb-src http://archive.ubuntu.com/ubuntu/ focal-updates universe
+
+## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
+## team, and may not be under a free licence. Please satisfy yourself as to
+## your rights to use the software. Also, please note that software in
+## multiverse WILL NOT receive any review or updates from the Ubuntu
+## security team.
+deb http://archive.ubuntu.com/ubuntu/ focal multiverse
+deb-src http://archive.ubuntu.com/ubuntu/ focal multiverse
+deb http://archive.ubuntu.com/ubuntu/ focal-updates multiverse
+deb-src http://archive.ubuntu.com/ubuntu/ focal-updates multiverse
+
+## N.B. software from this repository may not have been tested as
+## extensively as that contained in the main release, although it includes
+## newer versions of some applications which may provide useful features.
+## Also, please note that software in backports WILL NOT receive any review
+## or updates from the Ubuntu security team.
+# deb http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
+# deb-src http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
+
+## Uncomment the following two lines to add software from Canonical's
+## 'partner' repository.
+## This software is not part of Ubuntu, but is offered by Canonical and the
+## respective vendors as a service to Ubuntu users.
+# deb http://archive.canonical.com/ubuntu focal partner
+# deb-src http://archive.canonical.com/ubuntu focal partner
+
+deb http://security.ubuntu.com/ubuntu/ focal-security main restricted
+deb-src http://security.ubuntu.com/ubuntu/ focal-security main restricted
+deb http://security.ubuntu.com/ubuntu/ focal-security universe
+deb-src http://security.ubuntu.com/ubuntu/ focal-security universe
+deb http://security.ubuntu.com/ubuntu/ focal-security multiverse
+deb-src http://security.ubuntu.com/ubuntu/ focal-security multiverse

sources.list.arm

-deb http://ports.ubuntu.com/ubuntu-ports/ focal main restricted multiverse
-deb-src http://ports.ubuntu.com/ubuntu-ports/ focal main restricted multiverse
-deb http://ports.ubuntu.com/ubuntu-ports/ focal-updates main restricted multiverse
-deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-updates main restricted multiverse
+# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
+# newer versions of the distribution.
+deb http://ports.ubuntu.com/ubuntu-ports/ focal main restricted
+deb-src http://ports.ubuntu.com/ubuntu-ports/ focal main restricted
+
+## Major bug fix updates produced after the final release of the
+## distribution.
+deb http://ports.ubuntu.com/ubuntu-ports/ focal-updates main restricted
+deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-updates main restricted
+
+## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
+## team. Also, please note that software in universe WILL NOT receive any
+## review or updates from the Ubuntu security team.
 deb http://ports.ubuntu.com/ubuntu-ports/ focal universe
 deb-src http://ports.ubuntu.com/ubuntu-ports/ focal universe
 deb http://ports.ubuntu.com/ubuntu-ports/ focal-updates universe
 deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-updates universe
-deb http://ports.ubuntu.com/ubuntu-ports/ focal-security main restricted multiverse
-deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-security main restricted multiverse
+
+## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
+## team, and may not be under a free licence. Please satisfy yourself as to
+## your rights to use the software. Also, please note that software in
+## multiverse WILL NOT receive any review or updates from the Ubuntu
+## security team.
+deb http://ports.ubuntu.com/ubuntu-ports/ focal multiverse
+deb-src http://ports.ubuntu.com/ubuntu-ports/ focal multiverse
+deb http://ports.ubuntu.com/ubuntu-ports/ focal-updates multiverse
+deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-updates multiverse
+
+## N.B. software from this repository may not have been tested as
+## extensively as that contained in the main release, although it includes
+## newer versions of some applications which may provide useful features.
+## Also, please note that software in backports WILL NOT receive any review
+## or updates from the Ubuntu security team.
+# deb http://ports.ubuntu.com/ubuntu-ports/ focal-backports main restricted universe multiverse
+# deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-backports main restricted universe multiverse
+
+## Uncomment the following two lines to add software from Canonical's
+## 'partner' repository.
+## This software is not part of Ubuntu, but is offered by Canonical and the
+## respective vendors as a service to Ubuntu users.
+# deb http://archive.canonical.com/ubuntu focal partner
+# deb-src http://archive.canonical.com/ubuntu focal partner
+
+deb http://ports.ubuntu.com/ubuntu-ports/ focal-security main restricted
+deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-security main restricted
 deb http://ports.ubuntu.com/ubuntu-ports/ focal-security universe
 deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-security universe
+deb http://ports.ubuntu.com/ubuntu-ports/ focal-security multiverse
+deb-src http://ports.ubuntu.com/ubuntu-ports/ focal-security multiverse