In our application, it would be helpful if members could include their personal contact information, including mailing address, in their profile which could then be downloaded for snail mail and contact lists.
Not sure how/if GDPR would come into play, but since it would be voluntary it should not be a problem.
Here is my suggestion:
In the profile have the following optional fields:
City, State, Zip
In the Admin Settings, there would be a checkbox that says “Include personal contact information in the member profile.” The box would default to un-checked so those groups who do not want to collect personal information would not be affected.
Then if this could be downloaded as an Excel (or CSV) file it could then be easily used for mailing.