It looks like registering for Arxiv involves naming your institution but it is not described as a strict requirement. Why not give it a shot? Take a direct approach. Try to mimic the tone they are used to and be respectful, acting like you belong can go a long way. I imagine that existing work would be valued over soft qualifications. If you have work that belongs there I can’t see why they would turn you away. Try the same thing with other publishers that interest you.
It looks like registering for Arxiv involves naming your institution but it is not described as a strict requirement. Why not give it a shot? Take a direct approach. Try to mimic the tone they are used to and be respectful, acting like you belong can go a long way. I imagine that existing work would be valued over soft qualifications. If you have work that belongs there I can’t see why they would turn you away. Try the same thing with other publishers that interest you.