My mistake. I thought the fix was included in the last installer, but in fact, I applied it by hand with the following command :
sed -i 's/DEM.srtm3GeoTiffDEM_HTTP.*/DEM.srtm3GeoTiffDEM_HTTP = http:\/\/skywatch-auxdata.s3-us-west-2.amazonaws.com\/dem\/SRTM90\/tiff\//' /usr/local/snap/etc/snap.auxdata.properties
Now, the two commands runs well. I will do further tests in real conditions.
Thanks a lot for you support !