The most user-friendly option. Drag your .nds file into OpenEmu (which bundles DeSmuME internally) and play instantly.
While Archive.org is safer than 99% of ROM sites, no online activity is 100% risk-free. nintendo ds roms archive.org
Crucially, Archive.org operates under copyright exceptions like and "software preservation." Unlike torrent sites filled with malware, Archive.org is legally registered in the United States. However, this does not mean every file on the site is legal to download. The most user-friendly option