The first thing I had to do was reproduce the issue. So on my Windows 10 test VM I installed the Windows Subsystem for Linux, steps to do so are here and I installed the Ubuntu app.
Then, I fired up a bash shell using WSL and then I installed SQL Server on Linux for Ubuntu as documented here.
Now, I completed the installation of SQL Server on Linux using mssql-conf when that program completes it attempts to start SQL Server on Linux. BOOM! I’m able to reproduce the same error.
Looking at the error, I decided to see if I could run SQL Server on Linux from the shell as the user mssql. This would remove systemd and mssql-conf from the picture. Basically I wanted to see if I could get another, more descriptive, error to pop out.
Anthony digs out a very useful debugging tool in Linux, strace. Sadly, he’s not able to solve the problem at the moment, but at least gets us a step in the right direction.