Now we have T85291, let's document it.
The HTMLForm wiki page mentions the 'ooui format
classHTMLForm documents the $availableSubclassDisplayFormats value ooui, but the comment for it is identical to $availableDisplayFormats: "Available formats in which to display the form. " AIUI you can setDisplayFormat() to some formats, but ooui and vform must be set via HTMLForm::factory().
Point to any shipping code using ooui with HTMLForm.
We should ship the source code listed in HTMLForm and HTMLForm/tutorial wiki pages with the examples extension.
If I add the code in HTMLForm "Example usage" to Boilerplate and add the 'ooui' factory line, I get
To assist T100270: Replace use of jQuery UI and MW UI with OOUI across all Wikimedia-deployed extensions and core we should probably explain how to convert existing HTMLForm code. As well as code guidance we need design guidance, e.g. remove section that produces the border lines, etc.