Let's encrypt without being able to automate

Hi,
I have an internal cluster, so I can only use DNS challenge ( correct me if I am wrong, please ), and more over I am not able to call any command to create TXT record on the DNS. How would I do that, then? I wouldn't mind to edit DNS entries every 3 months for the time being, until the folks extend the DNS API I have to use.

Cheers.