I had previously worked on starting systemd to spawn services that I use. This was hacky and prone to breakage, especially in edge cases. I tried a few different scripts, none of them worked in my particular environment. I then noticed a comment by an Ubuntu contributor didrocks from November 2021 which read "PoC of systemd on WSL at startup of an instance"
This led me to believe that my time is wasted as whatever solution I come up with will become depricated in the near future. As a result I have decided to focus my time elsewhere and leave it with this simple, yet still hacky, start up script.
Add the following to /etc/wsl.conf (I believe it requires Windows 11 or above for the WSL subsystem to support this).
Note: you cannot just invoke systemd here, it has to be run differently. Then you will have to deal with namespaces and if you use them for other things you can experience breakage.
[boot]
command = /etc/runAtStartup.sh
I use a simple logging script, its not pretty but it works.
Download the script, place at the location specified in the wsl.conf file and chmod 755 <script>
In Windows
wsl --shutdown
Restart WSL in your usual way. Check /var/log/bootlog.* to ensure services started.