Digital tickets are kind of a wild west situation because there is no 100% dominant standard and rules vary wildly between teams, and even at the same team from season to season.
For example, Washington's XFL Team accepts only digital tickets for games at Audi Field, and you can only show them digital tickets in your Apple Wallet (on an iPhone), the XFL app (which like 5 people have), or whatever Android's equivalent of the Apple Wallet is. You cannot show a screenshot of the ticket, nor can you show them a PDF from your email app, even though there are other places (like an MLB game or an airport) where showing a screenshot or a PDF attachment is just fine.