A new Sokoban group has been published at https://groups.io/g/sokoban.
Since the old one at Yahoo has closed this new group is a good alternative place to meet other Sokoban fans!
You can join that group at https://groups.io/g/sokoban/join
By the way: users who like Facebook can also join the new Facebook group: https://www.facebook.com/groups/539527933307469/
Hence, there are now two alternatives for the old yahoo group.