Kaggle
https://www.kaggle.com/datasets
UCI Machine Learning repository
http://archive.ics.uci.edu/ml/index.php
https://archive.ics.uci.edu/ml/datasets.html
Amazon public data sets
https://registry.opendata.aws/
Lists of data sets
https://elitedatascience.com/datasets
https://en.wikipedia.org/wiki/List_of_datasets_for_machine_learning_research