I've looked into the issues you, Tom Clerckx, were having
Regarding: Error: TypeError: cannot pickle '_thread._local' object
This error is likely some form of issue with your own usage of FormStyleDefault. My widgets refactor, which is what Massimo reverted, did not change the implementation of FormStyleDefault.clone() at all, and it works without issue in a app which does not modify FormStyleDefault.
Is it possible you updated it in some way which adds a _thread._local object? I cannot reproduce this error when testing on 1.20250915.1
Regarding:
TypeError: Widget.form_html() missing 1 required positional argument: 'self'This is an oversight in my widgets refactor: i forgot to update a part of the code dealing with those kinds of field-specific widgets to instantiate the widget.
My intention was that you pass a class if it's a new Widget subclass, and an instance for backwards compatibility with the older widgets.
Unless Jacinto Parga has some other errors, i'll fix this and re-do the PR.