Fullname field doesn't actually match with Mailchimp List.

Why has this not been resolved yet ... I don't want full name either.

This "nearly" works but is a bit buggy, it seems to be more to do with the Field tag, if the field tag is FNAME the jotform field will display Full Name (instead of First Name, Last name), if you change the field tag to MMERGE1 (or delete the default First name and last name and recreate them - as above) and then try the integration again it should work.

If you want to use the FNAME tag (to display the persons first name in a mailchimp email campaign), turn off the existing integration in jotform then in the mailchimp list change the first name field tag from MMERGE1 to FNAME, go back to jotform and run the mailchimp integration again.

This is a bit hacky but seems to do the job

Thank you for your update, Declynam, I'm sure it will be very useful to others wishing to perform similar connection between their JotForm form fields and MailChimp. I would just like to quote a part of my answer provided on your own dedicated support thread, so that anyone reading this can also keep it in mind. Here it is:

Yes, our system is primarily designed to forward our Full Name field to any integrated services that are asking for names. That is why the Full Name field is the one that is supported for integrating with MailChimp's name field.

If you wanted to match our regular Text Box fields separately - one as a first name, and the other as a last name - this is really not a supported behavior. I see that you've devised a clever workaround that you've also posted on the original support thread where you were basing your setup from:

https://www.jotform.com/answers/510021

The workaround depends on "tricking" the JotForm integration wizard that the field in MailChimp is a custom field, so a Text Box can be matched to it, and then it is reverted back to being a name field. Tricking our system that way is perfectly fine, especially so long that is working, but please keep in mind that there is a possibility the field mapping may break some time in the future if/when there are updates being done on the integration between JotForm and MailChimp.

This is not something that will necessarily break, but with any setup such that is not using default intended functionalities, there is a chance an update might cause it to start failing, so this is just something to keep in mind. Cheers. :)