There is no "share icon" on the context menu if you access photoprism server behind proxy using an IP Address.
It only appears if you access from the FQDN.

I have upgraded from an April to Oct release this evening. I could create share links previous versions when using internal IP Address to reach the server. Which is the most convenient way to get around the split-DNS issue with the proxy.

Note PHOTOPRISM_SITE_URL is set to the FQDN in my configuration.