Please, clarify the question. Does the question concern the issue of publishing published scientific texts on the Research Gate portal or publishing unpublished texts by posting them on the Research Gate portal and this is called publishing on the Research Gate portal?
I publish my published articles, scientific monographs and other scientific papers on the Research Gate portal. The Research Gate Portal is not a scientific publication but an online science portal that serves as a scientific knowledge base. It is possible on the Research Gate portal to publish unpublished texts as so-called preprint, however, this is not a formal publication but an informative publication of a working text, over which the author is still working and this text is intended for publication in a specific scientific publication or the editorial offices of scientific journals in the future.
Dear Dariusz Prokopowicz! Thanks for the answer and for the question! The question really requires clarification. I am interested in the situation when the author registered on this resource has published works, but, nevertheless, such an author does not post their / information about them in his profile. In this case, we are not talking about preprints.
In most cases, the publishers maintain the copyrights of published papers and they do not give the authors the right to post their papers on the different web-sites, including Research Gate. Authors in most cases, however, can upload draft versions of their work but not the final edited and published ones.