Natural Earth 1:110m Land polygons — public domain.
https://www.naturalearthdata.com/downloads/110m-physical-vectors/110m-land/
https://www.naturalearthdata.com/about/terms-of-use/
Derived locally from the supplied ne_110m_land.geojson as a 1.8-degree dot grid, equirectangular projection. Not a border or small-island reference.