I did that too. Same thing.
I used strace to try and find out the error.
It is precisely this that I get
“Cannot run as root user”
Hence why I thought maybe deleting that line from the binary would work.
I then thought it might have not have had an effect because I only changed the symbolic link to the original binary and then I changed the original one and tried again. No luck still.
It’s just odd. Maybe it’s a thing we can’t solve at this point, some sort of incompatibility between the steam app and xfce4. All my other apps open up just fine.