Hi @Peter_Schroder,
There’s currently no way to install system-wide packages unless you use the Docker environment, and we don’t provide a base image.
Depending on the package you want, it may be possible to do a local (not system-wide) installation and include that in your build, but you would have to reference that explicitly in your service. I don’t personally have experience with this, and it may be more trouble than it’s worth.
Out of curiosity, if you’re comfortable sharing, what is the package that you’d like to install?