How to generate two links for different domains for sharing files?


Im running Seafile Pro 7.1.4 and I set it up with a Dynu DDNS. I just found out that some sites like Facebook don’t allow links with Dynu domains but allow it with the free domain I got from my ISP. Because I might change my ISP I want to keep my Dynu domain as it is and would only like for Seafile to generate two links links for sharing files (one with Dynu domain and one with a domain from my ISP).
Here is how I have it now:

Hese is how I would like to have it:

Whats the best way to do this?

e.g. Nginx config for both domains. But links will only be created for the configured domain. Also uploading won’t work most probably from secondary domains but about that I am not sure.