fwiw, I am one of the few lucky people allowed to attend games at the moment due to my job. Whilst the checks before entering the ground make sense and we are all ordered to wear masks at all times, the amount of people in the stands who pull theirs down as soon as they sit down, wear it incorrectly or just don't bother wearing one at all has always surprised me.
Note that I tend to be at the part-time teams. No idea if mask wearing is more strict for FT clubs.