With Sphinx 8.1.0, footnotes can't stand on their own and have
referenced from somewhere:
/builds/isc-projects/bind9/doc/arm/general.rst:439: WARNING: Footnote [#] is not referenced. [ref.footnote]
/builds/isc-projects/bind9/doc/arm/general.rst:441: WARNING: Footnote [#] is not referenced. [ref.footnote]
/builds/isc-projects/bind9/doc/arm/general.rst:445: WARNING: Footnote [#] is not referenced. [ref.footnote]
/builds/isc-projects/bind9/doc/arm/general.rst:457: WARNING: Footnote [#] is not referenced. [ref.footnote]