Wow, this escalated quickly. The TreeSitter repo was archived by its owner, apparently after the linked conversation. The tldr: TreeSitter was never supposed to be stable yet, a user demanded that it stays compatible neovim v0.11 and I think this user must be using Debian :/
#neovim #treesitter
https://github.com/nvim-treesitter/nvim-treesitter/discussions/8627#discussioncomment-16440673.