Thank you Marc, I remembered the page but I was wondering if someone tried anything with this.
For the record, I find and setup an alternative for my use-case (health declaration)
In the end the user see a wiki page with a tracker wikiplugin with a smarty template (I had to use $f_nnn 🥴)
On save he is redirected to a another page that display the same item using a plugin List.
On this page I placed at the bottom Signature wikiplugin.
(I need to test the following from user use mobile point of view)
Once the signature saved the user as for instruction to save as PDF or print and give me the document. (in hand or send)
Extra step... but it should work.