Idea Workspaces are now called Idea Boards. Every board keeps its items, its team and who can open it.
The list of boards is at /idea-boards, and each board is at /idea-boards followed by its ID. Links and bookmarks to the old /idea-workspaces addresses open the same page at its new address, in the same team.
The Help article is now Use an Idea Board. Its old address opens the new one.