A bit of extra info: - `ts` stands for "tree-sitter", meaning this mode uses tree-sitter under the hood, which is, among other things, very performant. - There's support for the CommonMark spec and GFM, so things like `- [ ]` checkboxes and ~~strikethrough~~ work out of the box, along with many other small QoL features. - This mode is BUILT-IN, so no extra packages are needed. - This is currently in the experimental…
I think in 31 registering the file types isnt necessary any more, the mode opens automatically for me (and i did manually delete the old markdown-mode)
Just FYI, I think the comment you replied to is by the author of the mode and an upstream Emacs contributor, so I would assume their instructions are up to date for the 31 release.