So I was going through the steps you’ve outlined here and I am stuck at this point:
sed -e ‘s/work-qubesos/\[sys-builder\]/g’ -e ‘s/qubes-builder-dvm/\[sys-builder-dvm\]/g’ rpc/policy/50-qubesbuilder.policy > /home/user/policy
As of this writing, the available file in the qubes-builderv2 repository is rpc/policy/50-qubesbuilder.policy.j2. When I tried the workaround of copying it to rpc/policy/50-qubesbuilder.policy and proceeding, I realised later on that I had disabled paste via the global keyboard (I could still do Ctrl+Shift+C to copy).
I saw this thread which indicated that I would need to edit the `policy.j2` file further in order to make it suitable for running as is. Will come back and update if I succeed.