If I understand your request:
After a failed startup, and then attempting to run ‘brave-browser’ from the command line/terminal, it would be a good thing - especially for relatively new users of Linux OS - to see in the terminal window (command line) response, something like:
. . . Brave has locked the profile so that it doesn’t get corrupted. If you are sure that no other processes are using this profile, you can unlock the profile and relaunch Brave. To unlock now, using this terminal window that you now view, enter:
rm ~/.config/BraveSoftware/Brave-Browser/Singletonlock
BTW, you might want to edit the title of your Original Post, changing to:
Brave Browser (Linux) NO START - Singletonlock [I assume]
Future reference for Brave Community: