OK, first things first. I’ve written up my procedure for building uuu and Jumpdrive. Building uuu and Jumpdrive · Wiki · Librem5 / Librem 5 Community Wiki · GitLab
Could you be a guinea pig for me and test out those instructions? I guess a new VM would be ideal, so that you have a cleanskin starting point - and can throw it all away afterwards if the result is a mess. 
However if you don’t do any development work on Linux, your starting point may be fairly accurate anyway.
I know you don’t have your phone yet, but the build instructions should be OK for anyone with Linux to try.
Once we’re happy with the build instructions, I will write something up for using this software (which will be much fewer steps!).