A data repository is an IT system that stores data sets.
This post is an introduction to data repositories.
List of open data repositories
OpenML.org
OpenML.org
Kaggle Datasets
Kaggle Dataset official website
Papers with Code
Paperswithcode.com
UC Irvine Machine Learning Repository
https://archive.ics.uci.edu
https://archive.ics.uci.edu/datasets
AWS Open Data
Registry.opendata.aws
TensorFlow Datasets
Tensorflow.org/datasets
Metaportals with data
Dataportals.org
Dataportals.org
Opendatamonitor.eu
Opendatamonitor.eu
Wikipedia
List of datasets for machine-learning research
Where can I find large datasets open to the public? at Quora
Where can I find large datasets open to the public? at Quora