I already have the XPS 13"  9300 developer edition which came with 18.04 pre installed. I would also like to know if and when Dell will be supporting 20.04 so I can upgrade knowing the hardware will all still work and dell will help if anything goes wrong.

I heard that the fingerprint reader may start to get supported around Q2 this year so could that also be around the same time 20.04 is supported too? Since that has fingerprint reader support included.

18.04 is supported until 2023

They might publish an oem version for the xps in 20.04. No idea

Everything should work fine on 20.04. You can image your disk to make a backup. Then upgrade to 20.04 and add the additional repositories from Dell and see what happens.

I managed to find Dell's repositories list (dell.archive.canonical.com/updates/), but I'm not sure which 'focal' should I choose. Any ideas?

What's the difference between downloading from Ubuntu website the normal version and the Dell Oem version? 

I'm asking because I'm running Kubuntu 20.04 in my Dell Latitude 7390. (My Dell came with Windows 10. I just installed this in a second partition). 

But I had a lot of suspend issues with Ubuntu 20.04, so I switched to Kubuntu 20.04 ( I wonder if those OEM versions work better). 

20.04 codename is Focal Fossa

You should go in the dell-foca folder :

http://dell.archive.canonical.com/updates/dists/focal-dell/Release

To download or upgrade packages, you should be using apt and have your /etc/apt/sources.list properly configured.

When you buy the laptop directly with Ubuntu you get support for it, under Ubuntu

You get a Ubuntu + a few packages from Dell like "Dell Recovery" and "Dell Support Assistant" pre-loaded.

Benefiting from the support on Ubuntu requires (if I am not wrong) to buy the machine with a pre-loaded Linux (Ubuntu or RHEL). If you bought it with Windows, you are free to install 18.04 or 20.04 but you will not have the Ubuntu recovery partition nor those few specific Dell programs pre-loaded.

If upgrading from 18.04 to standard 20.04 (with the Dell repos), what are the commands to add the right Focal fossa lists?

http://dell.archive.canonical.com/updates/dists/focal-dell/Release

Thanks

You can upgrade: 

# Add dell drivers for focal fossa

sudo sh -c 'cat > /etc/apt/sources.list.d/focal-dell.list << EOF
deb http://dell.archive.canonical.com/updates/ focal-dell public
# deb-src http://dell.archive.canonical.com/updates/ focal-dell public

deb http://dell.archive.canonical.com/updates/ focal-oem public
# deb-src http://dell.archive.canonical.com/updates/ focal-oem public

deb http://dell.archive.canonical.com/updates/ focal-somerville public
# deb-src http://dell.archive.canonical.com/updates/ focal-somerville public

deb http://dell.archive.canonical.com/updates/ focal-somerville-melisa public
# deb-src http://dell.archive.canonical.com/updates focal-somerville-melisa public
EOF'

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F9FDA6BED73CDC22

sudo apt update -qq

sudo apt install git htop lame net-tools flatpak audacity \
openssh-server sshfs simplescreenrecorder nano \
vlc gthumb gnome-tweaks ubuntu-restricted-extras thunderbird \
python-is-python3 ffmpeg ufw \
gnome-tweak-tool spell synaptic -y -qq

# Install drivers
sudo apt install oem-somerville-melisa-meta libfprint-2-tod1-goodix oem-somerville-meta tlp-config -y

Makes fingerprint work on 9300 with ubuntu 20.04, however not on 7390.

I keep forgetting: what are somervile, melisa, caterpie and all that? should I just add all dell repos for focal or does it depend on my model? I really wish Dell were a bit more transparent that way....

If you have the proper apt configure and type :

sudo apt info oem-somerville-melisa-meta

It will tell you :

Package: oem-somerville-melisa-meta
Version: 20.04ubuntu12
Priority: optional
Section: misc
Maintainer: Commercial Engineering
Installed-Size: 17.4 kB
Depends: ubuntu-oem-keyring, linux-generic-hwe-20.04, oem-somerville-meta, oem-fix-audio-intel-disable-autosuspend, libfprint-2-tod1-goodix
Ubuntu-Oem-Kernel-Flavour: default
Modaliases: meta(pci:*sv00001028sd0000096Dbc0Csc05*)
Download-Size: 3,012 B
APT-Manual-Installed: yes
APT-Sources: http://dell.archive.canonical.com/updates focal-somerville-melisa/public amd64 Packages
Description: hardware support for Dell XPS 13 9300
This is a metapackage for Dell XPS 13 9300. It installs
packages needed to support this hardware fully.

N: There is 1 additional record. Please use the '-a' switch to see it

somerville-melisa == 9300