Good afternoon,
A free Vim9script tutorial is apparently a lacuna to be filled;
there are some assorted observations such as [0] and [1], but
something more systematic I could only find [2] which only shows
the source code which is mostly wrong as it declares vim9script but uses
legacy vimscript if one looks for example at 05_dictionaries.vim.
Ideal to get converts up to speed would be the readership of this mailing list
contributing to this pull request [3] for LearnXinYMinutes.
Enno