Thankyou for creating this RFC. I can see benefits specifically around reducing sub-domain hijacking if people use this correctly. I just noticed they have working examples in the appendix. I am adding these to some of my domains now.
The way this works is, the part of a CAA record in quotes can have parameters added to it. These have been little used until now so many may not be familiar with this syntax but it's always been in the CAA spec. The examples at the end of the linked RFC are accurate.
Ah wow, I did not catch that the parameters go inside the quoted issue string. My brain misread the examples as `issue "example.org"; validationmethods=dns-01`.
To Let's Encrypt, thanks for finally making this happen.