I went to watch a friendly game near Belfast on Saturday afternoon. It was a mainly terraced ground so plenty of room to stand. They took contact details for track and trace on way in and spaced people out.
I went more out of curiosity than anything but it was handled well and it showed to me that it can work. I see no logical reason why the gradual return to full stadiums can't start now.
I don't think it'll be full for a bit, as getting 50-60,000 people through while maintaining social distancing will be a push. The Spurs pilot is ultimately aiming for around half capacity.