The policy link lists, in some detail, how and where you may share your accepted manuscript—for example, on arxiv. I would not interpret their criteria to include Researchgate.
For the benefit of those who haven't submitted a manuscript before: the accepted version is just the preprint with improvements from the peer review process - and no "other publisher value-added contributions such as copy-editing, formatting, technical enhancements and (if relevant) pagination". Assuming the associate editor is a volunteer (true for the journal in question), Elsevier's only in-kind contribution at this point is their awful submission system, and the Chief editor's time in accepting the associate editor's decision... although the chief editor might also be a volunteer.