There's a mega thread about Yahoo! Email and folk that didn't login for months and found their stuff gone. I will not open another debate about that here.
This is about YAHOO! GROUPS and if you have content there, it's going away FAST!
"Beginning December 14, 2019:
All Groups will be made private and any content that was previously uploaded via the website will be removed. We believe privacy is critical and made this decision to better align with our overall principles.
If you would like to keep any of the content you’ve posted or stored in the past within your Yahoo Group, please download it by December 14" (2019)