Unfortunately I note that they have abandoned that effort.
I noticed that Ubuntu have a firefox-geckodriver package built from
their firefox source package, so perhaps that could be used:
https://launchpad.net/ubuntu/+search?text=firefox-geckodriver
https://bugs.launchpad.net/bugs/1831204
Here are the relevant parts of their debian/ directory:
debian/control.in:Package: @MOZ_PKG_NAME@-geckodriver
debian/control.in-Architecture: any
debian/control.in-Depends: ${shlibs:Depends},
debian/control.in- ${misc:Depends},
debian/control.in- @MOZ_PKG_NAME@ (= ${binary:Version})
debian/control.in:Description: Safe and easy web browser from Mozilla - geckodriver
debian/control.in- Firefox delivers safe, easy web browsing. A familiar user interface,
debian/control.in- enhanced security features including protection from online identity theft,
debian/control.in- and integrated search let you get the most out of the web.
debian/control.in- .
debian/control.in: This package contains geckodriver, a proxy for using W3C WebDriver-compatible
debian/control.in- clients (such as selenium) to interact with Gecko-based browsers. See
debian/control.in: https://firefox-source-docs.mozilla.org/testing/geckodriver/ for details.
debian/tests/control-Test-Command: timeout -v 600 debian/tests/firefox-version
debian/tests/control:Depends: coreutils, firefox, firefox-geckodriver, python3-apt, python3-selenium
debian/tests/control-
debian/tests/control-Test-Command: timeout -v 600 debian/tests/html5test
debian/tests/control:Depends: coreutils, firefox, firefox-geckodriver, python3-selenium
debian/tests/control-Restrictions: allow-stderr
debian/build/rules.mk:install-geckodriver: debian/stamp-installgeckodriver
debian/build/rules.mk:debian/stamp-installgeckodriver: debian/stamp-makefile-install
debian/build/rules.mk: install -D $(MOZ_DISTDIR)/bin/geckodriver $(CURDIR)/debian/$(MOZ_PKG_NAME)-geckodriver/usr/bin/geckodriver
debian/build/rules.mk- @touch $@
...
debian/build/rules.mk:common-install-arch:: install-geckodriver