The antonyms for "computer expert" vary depending on the context. For instance, if you are in a group consisting of people who are technically-challenged, the antonyms could be "computer novice," "computer illiterate," or "technologically challenged." On the other hand, if you are exploring the field of electronics or information technology, the antonyms could be "mechanic," "technician," or "technologist."
In addition, if you are looking for a word with a negative connotation regarding technology, you might consider "luddite," meaning someone opposed to or disdainful of technological change. Similarly, some people might prefer to use the term "technophobe," meaning someone with an irrational fear of technology.