Slippy map tiles are square or rectangular images that follow a coordinate system defined by a grid called Tile Matrix: docs.opengeospatial.org/is/17-083r2/17-083r2.html. The Web Mercator grid is the de facto standard for Web maps. Made popular by google since 2005, it has pros and cons and:

With any such projection, some distortion is unavoidable. In the Mercator projection, geographical features further from the equator are exaggerated in size. For example, Greenland appears to be of a similar size to Africa. However, Africa is actually more than 14 times as large (by area).

ref: developer.tomtom.com/blog/decoded/understanding-map-tile-grids-and-zoom-levels

As one of the first requirements, we built TiTiler with support for serving tiles in multiple Projections by using rio-tiler and morecantile which provide the low level TileMatrixSets support.

$ curl | jq '.tileMatrixSets[] | .id'

You can easily add more TileMatrixSet support, see custom tms.

Notebook: Working_with_nonWebMercatorTMS