The maintainer released Yarn 2. Yarn 2 is pretty foundationaly different than Yarn 1, and can and does break a lot of products/projects if used. Some folks are not happy about it, although Yarn 1 will probably continue to be maintained by the community for a while.
This seems to be pretty fair about the whole thing: https://shift.infinite.red/yarn-1-vs-yarn-2-vs-npm-a69ccf022...