There are a number of repos under the https://github.com/toolforge org account which are mirrors of source repos here on Phabricator. Mirroring worked at some point in the past, but seems to also have stopped working quite a while ago.
I noticed this when I tried to setup https://github.com/toolforge/tool-k8s-status as a mirror of https://phabricator.wikimedia.org/source/tool-k8s-status/. There is no data at all in the sync logs (at least that I can see): https://phabricator.wikimedia.org/diffusion/synclog/?repositories=PHID-REPO-w6zrl6ar7bwdqkfcqdgj