Robert Woods - Users can still log into to OWA via the mobile web browser and get the same experience the OWA for devices app provided.
If you follow the steps in https://blogs.office.com/en-us/2013/09/04/configuring-delegate-access-in-outlook-web-app/ using a desktop browser, OWA in a mobile browser will display the shared folders.
Also, Outlook for iOS and Android supports shared/delegate calendars for Exchange Online mailboxes. See
https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsupport.office.com%2Fen-us%2Farticle%2Fcalendar-sharing-in-office-365-b576ecc3-0945-4d75-85f1-5efafb8a37b4%3Fui%3Den-US%26rs%3Den-US%26ad%3DUS&data=04%7C01%7Crosssmi%40exchange.microsoft.com%7Cc14ef53d25c14a87e3d108d5748c08f2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636543067179467770%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwifQ%3D%3D%7C-1&sdata=eXfe5xM%2Bb6JewBJMvkm5ZnKwtW1%2Bxczrr0mb3zhPtrA%3D&reserved=0