Government jobs are listed at usajobs.gov
This site lists a huge amount of government positions. You have to do some finessing with search terms; make sure you search using different terms. For instance I looked up art, design, visual, 3D, and got slightly different results for all four terms, with some overlap and some just different positions, but all four had at least some jobs that were related to digital art. Also be aware that some positions are only open to veterans, so pay attention to their posting information.
Here are some examples:
Visual Information Specialist for the Coast Guard (digital artist position) https://www.usajobs.gov/GetJob/ViewDetails/564742300
Artist/Illustrators for the army: https://www.usajobs.gov/GetJob/ViewDetails/555984500
Visual Information specialist: https://www.usajobs.gov/GetJob/ViewDetails/564745400
78 pages of positions related to software engineer. https://www.usajobs.gov/Search/?k=software&p=1