Anomaly detection without seasonality - is it possible?

Hi guys good evening, I have some time related data e.g., customer complaints overtime. Now there is no seasonality to this data. I am able to use Menn-Kendall test to check for upwards and downwards trends, but I was wondering is there an anomaly detection algorithm that doesn't depend on seasonality? or any other research you can point me to on the topic? I am reading about isolation forest and SSA time series decomp to see if they are helpful, …

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