Can Shapley/Lime values be used for unsupervised learning?
I don't think so, not directly. SHAP is trying to explain each feature's effect on the prediction, but you have no label here. It might be better to ask therefore, what are you trying to explain?
In the case of an isolation forest, you can find the short path through the trees to any anomaly. That path tells you why the trees separated it, based on what features. It may not be super interpretable, but can be read off directly.