DNSSEC is still active on the domain according to .ch whois. It appears the name servers are currently set to those of Netlify. You’ll need to configure the default GoDaddy name servers in order to disable DNSSEC. Once it is disabled you can then add the name to Netlify DNS.
As Netlify doesn’t support DNSSEC at any level unfortunately (see feature request opened in 2019 and this topic) the other option is to use external DNS configuration so you can continue to use DNSSEC.