Let's Encrypt has issued plenty of certificates for .farm TLDs.
If you are getting that error, it's because of something else, like errant characters or typos in the domain name being provided to the Let's Encrypt client.
Does it literally say *.domain in the error message? Or did it say something else?
Here are the commands i am running in their sequence followed by the output:
bitnami@ip-:~ DOMAIN=rera.farm
bitnami@ip-*********:~ WILDCARD=.DOMAIN
bitnami@ip-:~$ sudo certbot -d $DOMAIN -d $WILDCARD --manual --preferred-challenges dns certonly
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator manual, Installer None
Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org
Obtaining a new certificate
An unexpected error occurred:Error creating new order :: Cannot issue for ".domain": Domain name does not end with a valid public suffix (TLD)
Please see the logfiles in /var/log/letsencrypt for more details.