UC Irvine Machine Learning Repository

https://archive.ics.uci.edu

Kaggle

https://www.kaggle.com/datasets

OpenML

https://openml.org/search?type=data&sort=runs&status=active

Data.Gov

https://catalog.data.gov/dataset/?tags=machine-learning

Wikipedia list

https://en.wikipedia.org/wiki/List_of_datasets_for_machine-learning_research

GeeksForGeeks list

https://www.geeksforgeeks.org/top-machine-learning-dataset-find-open-datasets/

Carnegie Mellon University list

https://guides.library.cmu.edu/artificial-intelligence/datasets

Examples of Persistent Homology on Point Clouds