I do not use docker, but in this post we see a very experienced builder comment that this mechanism is broken for community users Can't find extract-files.sh/can't run it while following "How to Build the /e/ ROM?" page - #9 by petefoth, suggesting (effectively) that one should include
the flag INCLUDE_PROPRIETARY=true
as also Can't build for Oneplus Nord (avicii) - #3 by petefoth
The variable would be defined as
-e "INCLUDE_PROPRIETARY=true"
… and of course can do no harm.