Hi. Version 5.0.26-3 of this package successfully built ok for me in trixie today, before 5.0.26-4 propagated to testing.
This is probably because python3-sphinx-rtd-theme was updated. So, the change you did here is probably not necessary anymore (but you might want to double-check). (This is just FYI, I'm not going to file another bug for that). Thanks.
