Not a particularly complex project.

Just some work trying to find the population in a given metro that lives in a census block or equivalent with over 3,000 people/km This was done in Canada, Singapore, and Europe using their census data, GIS, and Geofeather.

Note that there was a file named grid_1km_surf.feather sourced from the European Union in the data folder, but was removed from being too big. You can find the GPKG version here, and then convert it to feather.