SCC in Undirected Graphs?

SCCs only make sense for directed graphs where edges have direction. In an undirected graph, if you can reach node $v$ from node $u$, you can always reach $u$ from $v$ by reversing the path. Every connected component in an undirected graph is trivially "strongly connected".

For undirected graphs, use simple DFS or BFS to find connected components in $O(V + E)$ time. No need for SCC algorithms like Kosaraju or Tarjan.

Space complexity is $O(V)$ for the data structures used.