This is the netCDF file which is used for the regional masks: NSIDC-0780_SeaIceRegions_EASE2-N25km_v1.0.nc and this is the one with the land/ice/ocean mask: EASE2_N25km.LOCImask_land50_coast0km.720x720.bin

What if you replace ccrs.NorthPolarStereo() with ccrs.LambertAzimuthalEqualArea ?

Unfortunately doesn't work:

ccrs.LambertAzimuthalEqualArea(central_longitude=0.0, central_latitude=-90.0)

Awesome, thanks Lars! central_latitude needs to be 90, not -90, but with this it works like a charm :-)

EASE2=LambertAzimuthalEqualArea not NorthPolarStereo