It’s getting a bit further this time, it’s finding conda’s version of boost now (but only the boost headers, not the libraries).
I had this working on Ubuntu 20.04, but I’ll try Ubuntu 18.04 (same as you) and see if I can reproduce this.
One thing you can try in the meantime is to also install cmake via conda (conda install cmake) and then run cmake again - I don’t anticipate this’ll make too much difference but worth a try.
And as Michael noted, the CMAKE_PREFIX_PATH is how we’re currently forcing CMake to use the dependencies from conda (instead of the system).