I've solved it. Had to run as root to get it to work.

Sorry, I should have clarified. Trying to install from Mac and Linux/Ubunutu 18.04 on to Nexus 5. Mac installer doesn't even see the device even though I can run fastboot device and it recognizes it. Linux sees it then installs the UBPort recovery but then refuses to continue installation.

event though it's in the UBports recovery mode. it's like it's not seeing it anymore after it installs recovery. what am i missing?