Recently, I have read new papers and seen new different approaches and the very interesting physical effects in alternatives to general relativity, and I think I see a bit of ideas for future papers, but I don't have any expertise in these approaches, I have published papers only in general relativity(from physics point of view). At my university, no one is interested in these topics(general relativity or alternatives, only on numerical simulations of hot plasma in accretion disks around black holes). I have proposed some ideas to some friends and peers and although at first sight they seem to be very interested, after I send them the differential equations and papers to be studied everyone lost interest. The question would be how to find a collaborator interested in such a new approach that would lead to papers in good journals where I have published before?
The best place to begin to look for collaborators are researchers who are currently publishing in your topic/field of interest. I would recommend contacting the authors of journal articles you read and can contribute to the topic in a significant manner (enough to be published). Contact the researcher and suggest a collaboration, with what skills and expertise you bring to the table and your intended result of collaboration.