I have the app on my phone anyway so it'd easy enough to show proof of having the jabs. I'll have to have my phone to get into the ground anyway as it's got my ticket on.
Only concern is how efficient the people are doing the checks. I remember at the first game of the season a few years back, they were doing enhanced security checks to get into the ground and they were that slow loads of us nearly missed kick off. They just stopped doing them after a while and just let everyone in as the queue was massive, as it was taking too long.