As an Owner or Admin, if you find that group members are changing the theme too frequently, you can lock the chat theme for all members.
To lock a chat theme:
- As an Owner or Admin, open the group chat you want to lock the theme for
- Tap the group's name in the top bar
- Enable the Lock Chat Theme toggle
- Tap Lock
Now, only other Owners or Admins are able to change the chat theme, regular group members won't be able to.
As a group member, you'll see a message letting you know that the chat theme is locked and can't be changed.