There isn't a way to externally sign/validate a TXT record, that I know of.
A TXT record may be used in the signing process if using DNS verification, but you are getting a certificate for the name overall so using an A record to hold the hash you are looking to certify does the trick, then if you want to use HTTP-01 for verification rather than an extra DNS record you can.
A TXT record may be used in the signing process if using DNS verification, but you are getting a certificate for the name overall so using an A record to hold the hash you are looking to certify does the trick, then if you want to use HTTP-01 for verification rather than an extra DNS record you can.