After setting 'org-export-with-footnotes' to 'nil', the space following the footnote is removed when exporting (I’ve tested this with pandoc [docx and html]).
So, given this example: «Pellentesque dapibus suscipit ligula.[fn:1] Donec posuere augue in quam.» The resulting text is: «Pellentesque dapibus suscipit ligula.Donec posuere augue in quam.» The only way in which I can get a space in the correct place is by putting an extra one before the footnote. Emacs : GNU Emacs 28.0.91 (build 1, aarch64-apple-darwin21.2.0, NS appkit-2113.20 Version 12.1 (Build 21C52)) of 2022-02-06 Package: Org mode version 9.6.1 ( @ /Users/test/.emacs.d/elpa/28.0/develop/org-9.6.1/)