Pull requests are not optional on GitHub. Users have been begging for more than a decade for an option to disable pull request for a repository, and GitHub continues to ignore them.
As another poster noted, you can disable it by limiting all interactions (6 months at a time). It is not ideal, but it does work to for PRs. You should also close all current PRs when you do that so users cannot push to those branches as well.
As another poster noted, you can disable it by limiting all interactions (6 months at a time). It is not ideal, but it does work to for PRs. You should also close all current PRs when you do that so users cannot push to those branches as well.