diff --git a/build_debian.sh b/build_debian.sh
index 38d0fb0330..5686cbf0ac 100755
--- a/build_debian.sh
+++ b/build_debian.sh
@@ -281,8 +281,7 @@ sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y in
     dbus                    \
     ntpstat                 \
     openssh-server          \
-    python                  \
-    python-apt              \
+    python3-apt             \
     traceroute              \
     iputils-ping            \
     net-tools               \
@@ -314,12 +313,12 @@ sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y in
     ndisc6                  \
     makedumpfile            \
     conntrack               \
-    python-pip              \
     python3                 \
     python3-distutils       \
     python3-pip             \
+    python-is-python3       \
     cron                    \
-    libprotobuf17           \
+    libprotobuf23           \
     libgrpc++               \
     haveged                 \
     jq
@@ -350,9 +349,7 @@ sudo sed -i '/^#.* en_US.* /s/^#//' $FILESYSTEM_ROOT/etc/locale.gen && \
 sudo LANG=en_US.UTF-8 DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT update-locale "LANG=en_US.UTF-8"
 sudo LANG=C chroot $FILESYSTEM_ROOT bash -c "find /usr/share/i18n/locales/ ! -name 'en_US' -type f -exec rm -f {} +"
 
-# Install certain fundamental packages from $IMAGE_DISTRO-backports in order to get
-# more up-to-date (but potentially less stable) versions
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y -t $IMAGE_DISTRO-backports install \
+sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install \
     picocom \
     systemd \
     systemd-sysv
@@ -425,13 +422,10 @@ done < files/image_config/sysctl/sysctl-net.conf
 sudo augtool --autosave "$sysctl_net_cmd_string" -r $FILESYSTEM_ROOT
 
 # Upgrade pip via PyPI and uninstall the Debian version
-sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip2 install --upgrade 'pip<21'
 sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install --upgrade pip
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get purge -y python-pip python3-pip
+sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get purge -y python3-pip
 
 # For building Python packages
-sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip2 install 'setuptools==40.8.0'
-sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip2 install 'wheel==0.35.1'
 sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install 'setuptools==49.6.00'
 sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install 'wheel==0.35.1'
 
diff --git a/files/apt/sources.list.amd64 b/files/apt/sources.list.amd64
index 45902be107..108bf0dd59 100644
--- a/files/apt/sources.list.amd64
+++ b/files/apt/sources.list.amd64
@@ -1,13 +1,13 @@
 ## Debian mirror on Microsoft Azure
 ## Ref: http://debian-archive.trafficmanager.net/
 
-deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ buster main contrib non-free
-deb-src [arch=amd64] http://debian-archive.trafficmanager.net/debian/ buster main contrib non-free
-deb [arch=amd64] http://debian-archive.trafficmanager.net/debian-security/ buster/updates main contrib non-free
-deb-src [arch=amd64] http://debian-archive.trafficmanager.net/debian-security/ buster/updates main contrib non-free
-deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ buster-backports main contrib non-free
-deb [arch=amd64] http://packages.trafficmanager.net/debian/debian buster main contrib non-free
-deb-src [arch=amd64] http://packages.trafficmanager.net/debian/debian buster main contrib non-free
-deb [arch=amd64] http://packages.trafficmanager.net/debian/debian-security/ buster_updates main contrib non-free
-deb-src [arch=amd64] http://packages.trafficmanager.net/debian/debian-security/ buster_updates main contrib non-free
-deb [arch=amd64] http://packages.trafficmanager.net/debian/debian buster-backports main contrib non-free
+deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ bullseye main contrib non-free
+deb-src [arch=amd64] http://debian-archive.trafficmanager.net/debian/ bullseye main contrib non-free
+#deb [arch=amd64] http://debian-archive.trafficmanager.net/debian-security/ bullseye/updates main contrib non-free
+#deb-src [arch=amd64] http://debian-archive.trafficmanager.net/debian-security/ bullseye/updates main contrib non-free
+#deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ bullseye-backports main contrib non-free
+#deb [arch=amd64] http://packages.trafficmanager.net/debian/debian bullseye main contrib non-free
+#deb-src [arch=amd64] http://packages.trafficmanager.net/debian/debian bullseye main contrib non-free
+#deb [arch=amd64] http://packages.trafficmanager.net/debian/debian-security/ bullseye_updates main contrib non-free
+#deb-src [arch=amd64] http://packages.trafficmanager.net/debian/debian-security/ bullseye_updates main contrib non-free
+#deb [arch=amd64] http://packages.trafficmanager.net/debian/debian bullseye-backports main contrib non-free
diff --git a/files/build_templates/sonic_debian_extension.j2 b/files/build_templates/sonic_debian_extension.j2
index 0867d07933..deb34dd302 100644
--- a/files/build_templates/sonic_debian_extension.j2
+++ b/files/build_templates/sonic_debian_extension.j2
@@ -144,8 +144,6 @@ sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip2 install ipaddr
 sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install ipaddr
 
 # Install Python module for grpcio and grpcio-toole
-sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip install "grpcio==1.39.0"
-sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip install "grpcio-tools==1.39.0"
 sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install "grpcio==1.39.0"
 sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install "grpcio-tools==1.39.0"
 
@@ -281,12 +279,10 @@ sudo cp -f $IMAGE_CONFIGS/bash/bash.bashrc $FILESYSTEM_ROOT/etc/
 
 # Install prerequisites needed for installing the dependent Python packages of sonic-host-services
 # These packages can be uninstalled after installation
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install libcairo2-dev libdbus-1-dev libgirepository1.0-dev pkg-config
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y -t $IMAGE_DISTRO-backports install libsystemd-dev
+sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install libcairo2-dev libdbus-1-dev libgirepository1.0-dev libsystemd-dev pkg-config
 
-# Manually install runtime dependencies to avoid them being auto-removed while uninstalling build dependencies
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install gir1.2-glib-2.0 libdbus-1-3 libgirepository-1.0-1
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y -t $IMAGE_DISTRO-backports install libsystemd0
+# Mark runtime dependencies as manually installed to avoid them being auto-removed while uninstalling build dependencies
+sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-mark manual gir1.2-glib-2.0 libdbus-1-3 libgirepository-1.0-1 libsystemd0
 
 # Install SONiC host services package
 SONIC_HOST_SERVICES_PY3_WHEEL_NAME=$(basename {{sonic_host_services_py3_wheel_path}})
@@ -340,7 +336,7 @@ sudo sed -i -e '/^passwd/s/ radius//' $FILESYSTEM_ROOT/etc/nsswitch.conf
 # Install a custom version of kdump-tools  (and its dependencies via 'apt-get -y install -f')
 if [[ $CONFIGURED_ARCH == amd64 ]]; then
 sudo DEBIAN_FRONTEND=noninteractive dpkg --root=$FILESYSTEM_ROOT -i $debs_path/kdump-tools_*.deb || \
-    sudo LANG=C DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true chroot $FILESYSTEM_ROOT apt-get -q --no-install-suggests --no-install-recommends --force-no install
+    sudo LANG=C DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true chroot $FILESYSTEM_ROOT apt-get -q --no-install-suggests --no-install-recommends install
     cat $IMAGE_CONFIGS/kdump/kdump-tools | sudo tee -a $FILESYSTEM_ROOT/etc/default/kdump-tools > /dev/null
 fi
 
@@ -854,7 +850,7 @@ sudo LANG=C chroot $FILESYSTEM_ROOT systemctl enable sonic.target
 sudo cp $BUILD_TEMPLATES/sonic-delayed.target $FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM
 sudo LANG=C chroot $FILESYSTEM_ROOT systemctl enable sonic-delayed.target
 
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get purge -y python-dev python3-dev
+sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get purge -y python3-dev
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get purge -y build-essential libssl-dev swig
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get purge -y libcairo2-dev libdbus-1-dev libgirepository1.0-dev libsystemd-dev pkg-config
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get clean -y
diff --git a/files/image_config/apt/sources.list.d/amd64/debian_archive_trafficmanager_net_debian.list b/files/image_config/apt/sources.list.d/amd64/debian_archive_trafficmanager_net_debian.list
index d35c618112..db55f3dd60 100644
--- a/files/image_config/apt/sources.list.d/amd64/debian_archive_trafficmanager_net_debian.list
+++ b/files/image_config/apt/sources.list.d/amd64/debian_archive_trafficmanager_net_debian.list
@@ -1,3 +1,3 @@
-deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ buster main contrib non-free
-deb [arch=amd64] http://debian-archive.trafficmanager.net/debian-security/ buster/updates main contrib non-free
-deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ buster-backports main contrib non-free
+deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ bullseye main contrib non-free
+#deb [arch=amd64] http://debian-archive.trafficmanager.net/debian-security/ bullseye/updates main contrib non-free
+deb [arch=amd64] http://debian-archive.trafficmanager.net/debian/ bullseye-backports main contrib non-free