Last season, my last (at the moment, may go back next season), the leagues I was on was all different.
Some were still using paper copies, some were using the app Comet, whilst one done both (in case the app failed).
With regards to the app, some leagues were asking teams to complete the team lines the day before, few days before, whereas another was happy as long it was completed by end of the match (but handed the ref a paper copy). The idea of the app can be great, but how does a youth team manager know 24+ hours ahead of the match who is playing, what condition the players will be in and what if something happens en route, or during warm up? It is harder to change on the app than a piece of paper.