I will not participate in #Hacktoberfest this year, although contributing to #OpenSource and #FreeSoftware is my day job. First, I already have enough t-shirts. But second, the ecosystem I use on a daily basis is mostly made up of projects that use GitLab, or BitBucket, or sr.ht, or Fossil, or sending patches by mail, or GNU Savannah, or (good grief!) even SourceForge. I think only two of the projects I contributed last year were on GitHub.
The #FOSS world is so much bigger. Don't forget that.