This doesn't answer your question completely, but the user group communities are very strong for both IBM Mainframe and IBM i platforms. https://www.share.org/

This doesn't answer your question completely, but the user group communities are very strong for both IBM Mainframe and IBM i platforms. https://www.share.org/ https://www.share.org/ and https://www.gse.org https://www.gse.org for example.