Unexpected opam version (found: , expected: 2.0.0~rc3). Stop.
Fixed by installing Ubuntu version of opam then:
opam init eval `opam config env`
opam pin add opam-devel --dev
sudo cp /home/leo/.opam/system/lib/opam-devel/* /usr/local/bin
source .profile
Would have saved me a lot of time mucking around having these in instructions for Ubuntu.
Edited by moneyevery3days