These are my Raspberry Pi 4 and 400 resources that I have collected. I imagine this will likely be somewhat of a messy disarray of digital scribbles for some time. Feel free to pile on anything that may be helpful. For the most part if I refer to the 400, I also mean the 4 as well.
General Purpose
This is my section for any general purpose computing images built for the Pi 4 platform.
openSUSE Builds of the Raspberry Pi 4 and 400. I have run these on both.
openSUSE Raspberry Pi 4 Images for Tumbleweed and Leap
Recommended List of Applications
In order to use the Raspberry Pi 4 or 400 as you would with Raspberry Pi OS but using openSUSE as your operating system. Here is the list of applications you can use to have all the fun and educational exploration of the Raspberry Pi.
These packages are in the official repository. libgpiod are for accessing the GPIO pins and Thonny is a Python IDE for beginners
sudo zypper -n install libgpiod thonny flatpak
See this page on the openSUSE wiki for more information on GPIO usage.
https://en.opensuse.org/openSUSE:GPIO
The next set of applications are distributed as Flatpak. By default, Flathub is not enabled, at least, at the time of writing. There are numerous ways to just turn it on but this is the easy way in the terminal.
Add Flathub Remote Repository
sudo flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
The Flatpak applications to install next is Scratch, a visual programming language, geared for kids and PyCharm Community Edition an IDE for professional developers. That is not actually in the Raspberry Pi default image but I really like it and so I am just including it because you will thank me later.
Install Scratch 3 Flatpak
sudo flatpak install --noninteractive --system edu.mit.Scratch
Install PyCharm Community edition Flatpak
sudo flatpak install --noninteractive --system com.jetbrains.PyCharm-Community
At this point. you can do all the fun, educational activities in the Raspberry Pi 400 Beginners guide.
Gaming
Images used specifically for the purpose of gaming.
RetroPi Retro Gaming Machine Image
References
https://en.opensuse.org/openSUSE:GPIO
https://flathub.org/apps/details/edu.mit.Scratch
https://software.opensuse.org/package/thonny
https://flathub.org/apps/details/com.jetbrains.PyCharm-Community
https://www.dbooks.org/raspberry-pi-beginners-guide-191204773x/