I believe the latest version of mesa has new Meson options to add/remove support for patented codecs at build-time:
https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/meson_options.txt

In general, has an effort been made to avoid patented codecs system-wide, or should I open a new ticket tracking this progress?

I think we might also need help from the FSF legal team to sort out issues relating to exactly what is patented and what is libre (ie. the patents are expired, or sometimes only cover encoding/decoding but not both).