Hi!
I released my spell-check addon in 2016 and wanted finally to update it, but - alas:
Your add-on failed validation with 1 error.
You cannot update a WebExtensions add-on with a legacy add-on. Your users would not be able to use your new version because Firefox does not support this type of update
(I did not notice when my simple extension turned into something different)
As I understand, I am required to do something more complex to achieve the same result - get the spell-check dic published.
Does any quick-guide exists, as the dic is the only thing I am interested about to get published.
As far as I know primarily the bundling format changed, which is why it was automatically converted on the server side. You should be able to just download the version currently on AMO, unzip it and check out the changes there.