Here are all of the clips I’ve been able to find thus far of significant pre-War or Wartime football. There are others – I’ve favoured clips that give at least a faint idea of play or an idea of the sort of people involved. If anyone can locate the 1912 West Ham v Manchester United clip that Youtube have deleted, I’d be delighted to see it.
Arsenal 1897 (Football in Hades: it doesn’t make it look like fun)
Blackburn v West Brom 1898 (Not much going on here, either)
FA Cup Final 1901 (Mark Holland of Blognor Regis’ ancestor visible here)
Please link to any more (legal) ones you may have in the comments.