root@node03:~# cat /etc/apt/sources.list.d/system76-release.list
deb http://apt.pop-os.org/release jammy main
root@node03:~# cat /etc/apt/preferences.d/99-custom
# https://wiki.debian.org/DebianRepository/UseThirdParty#Standard_pinning
# https://help.ubuntu.com/community/PinningHowto
# https://wiki.debian.org/AptConfiguration#Force_installation_of_a_package_from_a_repository
# apt-cache policy
# to see priorities, origins, releases, etc

# Never prefer packages from the my-custom-repo repository
Package: *
#Pin: origin apt.pop-os.org
Pin: release o=pop-os-release
Pin-Priority: 100

# Allow upgrading only my-specific-software from my-custom-repo
#Package: my-specific-software
#Pin: release o=pop-os-release
#Pin-Priority: 500

Package: system76-power
#Pin: origin apt.pop-os.org
Pin: release o=pop-os-release
Pin-Priority: 1000