Hi @Arturo,
If you want to use a ssl server block you need to specify a cert and a private key, you could create a self-signed certificate and use it as your default server so No SNI connections will reach this fake cert… or you can use the approach you are already using right now (with your real domain names oxxxxxx.club and kxxxxx.club) and it is use different ips for each domain.
Cheers,
sahsanu