Yeah I'm on 19, I tried this and it technically put the application on my home screen but when I click it it just says NO
Are you on fw 19? Some Nintendo changes broke forwarders. Check the last page on this thread. https://gbatemp.net/threads/nsp-forwarder-generator-an-online-tool-to-create-nro-retroarch-forwarders.630368/
This should work for fw 19 in the meantime.
https://nsp-forwarder-git-fork-masagrator-main-tootallteam.vercel.app/