GDPR Communication Preferences Compulsory
One route is to do the following:

Modify the section


  Communication Preferences
  We want to ensure we are only sending you information that is of interest to you, in a way you are happy to receive.


to make it clear that by signing up they are signing up to the Newsletter

then in Comms Pref settings page, untick the "Allow users to opt-in to mailing groups"

then on your MS Newsletter profile - use the Adv Settings to 'add them to group'

i think that makes it really clear what folk are signing up for
and removes the extra tickbox for the newsletter from the form