If you are using this server pack on a managed server, meaning you can not execute scripts, please use the fabric-server-launcher.jar instead of the fabric-server-launch.jar. Note the extra "er" at the end of "launcher".
This is the improved Fabric Server Launcher, which will take care of downloading and installing the Minecraft server and any and all libraries needed for running the Fabric server.

The downside of this method is the occasional incompatibility of mods with the Fabric version, as the new Fabric Server Launcher always uses the latest available Fabric version.
If a mod is incompatible with said latest Fabric version, contact the mod-author and ask them to remedy the situation.
The official Fabric Discord had the following to add to this:
    Fabric loader however is cross version, so unless there is a mod incompatibility (which usually involves the mod being broken / using non-api internals)
    there is no good reason to use anything but the latest. I.e. the latest loader on any Minecraft version works with the new server launcher.