You can add a url to your other server on the dashboard using this url handler with the “?server=” query param in the iOS app – https://companion.home-assistant.io/docs/integrations/url-handler/#define-server
So for example I link to homeassistant://navigate/lovelace/0?server=Summer%20House in my main house dashboard and homeassistant://navigate/lovelace/0?server=Home on the Summer House dashboard, i’m also using a conditional card to only show it on Mobile and it works great.