Hey there Web242,
Thanks for writing in here. I’d be glad to help take a look into things with you here.
After some testing, it looks like the best way to ensure that the HTML/Plain-Text option is added or removed is by navigating within the MailChimp account to “Lists > Select a list > Signup Forms > select or deselect checkbox for ‘Let subscriber pick email format (Plain-Text or HTML).'” From here, it will be necessary to go to Plugin Settings for “MailChimp”, select the list and click “Update List.” This will allow the List Subscribe Plugin to update based on any new changes in settings from the MailChimp app and should remove the HTML/Plain-Text option.
Glad to hear you were able to come up with a workaround here using CSS if that standard workflow does not work. In any case, I can see how having this option within the Plugin settings on the WordPress site would be helpful and would be glad to pass that feedback along to our team to keep in mind for the future.
If there’s anything else we can assist with, please don’t hesitate to let us know!
Thanks,
Malachite