Re-enable Dell repositories after upgrade to new Ubuntu release on XPS 13?

I have an Dell XPS 13 7390 laptop which came with Ubuntu 18.04. I responded Yes to a pop up asking if I wanted to upgrade to Ubuntu 20.04 (the new LTS release). Now I have a system on which all the Dell apt repositories are disabled. Apt was warning about not being able to upgrade firmware or something during a regular upgrade.

How do I enable the correct Dell repositories for my laptop and Ubuntu release?

Why does this problem exist in the first place?

Here is some command line output to illustrate the problem:

$ grep dell /etc/apt/sources.list.*/*
/etc/apt/sources.list.d/bionic-dell-beaver-three-eyed-raven.list:# deb http://dell.archive.canonical.com/updates/ bionic-dell-beaver-three-eyed-raven public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell-beaver-three-eyed-raven.list:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell-beaver-three-eyed-raven public
/etc/apt/sources.list.d/bionic-dell-beaver-three-eyed-raven.list.distUpgrade:# deb http://dell.archive.canonical.com/updates/ bionic-dell-beaver-three-eyed-raven public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell-beaver-three-eyed-raven.list.distUpgrade:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell-beaver-three-eyed-raven public
/etc/apt/sources.list.d/bionic-dell-beaver-three-eyed-raven.list.save:# deb http://dell.archive.canonical.com/updates/ bionic-dell-beaver-three-eyed-raven public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell-beaver-three-eyed-raven.list.save:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell-beaver-three-eyed-raven public
/etc/apt/sources.list.d/bionic-dell.list:# deb http://dell.archive.canonical.com/updates/ bionic-dell public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell.list:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell public
/etc/apt/sources.list.d/bionic-dell.list.distUpgrade:# deb http://dell.archive.canonical.com/updates/ bionic-dell public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell.list.distUpgrade:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell public
/etc/apt/sources.list.d/bionic-dell.list.save:# deb http://dell.archive.canonical.com/updates/ bionic-dell public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell.list.save:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell public
/etc/apt/sources.list.d/bionic-dell-service.list:# deb http://dell.archive.canonical.com/updates/ bionic-dell-service public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell-service.list:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell-service public
/etc/apt/sources.list.d/bionic-dell-service.list.distUpgrade:# deb http://dell.archive.canonical.com/updates/ bionic-dell-service public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell-service.list.distUpgrade:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell-service public
/etc/apt/sources.list.d/bionic-dell-service.list.save:# deb http://dell.archive.canonical.com/updates/ bionic-dell-service public # disabled on upgrade to focal
/etc/apt/sources.list.d/bionic-dell-service.list.save:# deb-src http://dell.archive.canonical.com/updates/ bionic-dell-service public
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list:deb http://dell.archive.canonical.com/ focal somerville
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list:# deb-src http://dell.archive.canonical.com/ focal somerville
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list:deb http://dell.archive.canonical.com/ focal somerville-three-eyed-raven
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list:# deb-src http://dell.archive.canonical.com/ focal somerville-three-eyed-raven
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.distUpgrade:deb http://dell.archive.canonical.com/ focal somerville
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.distUpgrade:# deb-src http://dell.archive.canonical.com/ focal somerville
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.distUpgrade:deb http://dell.archive.canonical.com/ focal somerville-three-eyed-raven
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.distUpgrade:# deb-src http://dell.archive.canonical.com/ focal somerville-three-eyed-raven
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.save:deb http://dell.archive.canonical.com/ focal somerville
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.save:# deb-src http://dell.archive.canonical.com/ focal somerville
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.save:deb http://dell.archive.canonical.com/ focal somerville-three-eyed-raven
/etc/apt/sources.list.d/oem-somerville-three-eyed-raven-meta.list.save:# deb-src http://dell.archive.canonical.com/ focal somerville-three-eyed-raven