Got it. There's a hidden .install4j folder in the unix download which didn't get copied when I first extracted the pack and moved the files to where I wanted them. This time I just extracted and copied the run file into the folder without moving anything else and it launched fine so did the ol' ls -a to check for hidden files and found it.
Thanks for the video tatsu; it was a big help
I did hit a snag when trying to launch the client however where it gives error:
Error: Could not find or load main class install4j.com.faforever.client.Main
Caused by: java.lang.ClassNotFoundException: install4j.com.faforever.client.Main
I'm on Ubuntu 20.04 and tried using both PPA as well as openjdk (made sure to set environment variable both times) and both gave same error. This is v1.2.0 stable unix release extracted to same folder as the Steam run file as shown in video.