Once a page is published from Replo does the app need to remain installed for the page to be used?
Technically when you click publish we push a liquid page template to your theme. So after uninstall this template would persist on your theme therefore making the page accessible after uninstall.
You can’t make edits to this page after uninstall AND the page won’t be supported going forward so any changes we make to our page rendering (JS libraries for example) won’t get updated. But generally yes it’s still accessible