Apparently Lee is organising GitHub Game-Off 2023, so that might be a place where you will be able to get some of his attention.
Go look into repo’s issue tracker and find all the posts where people say that they made a fork, or are in other ways interested in getting the repo more up to date. Then message them all, organise them together. Maybe even set up a Github Organisation (fancy name for a “group of users”), and when you have everything set in place, bother Lee until he transfers repo ownership to that organisation.