When I setup my new copy of little-link custom, I had to set that random salt value in the env file manually, since the version to click within the software wouldn't work for me.
I couldn't trace any reason why it wasn't working (there was no output in PHP's error_log) or any errors in apache2's log so I couldn't ultimately figure out what the root cause of the issue was, but I thought I'd better report that I'd had issue with it since it might confuse new (er) users, which from what I can tell is one of the design goals of this version :)
It was fixed by manually generating the salt and adding it to the .env file.
Kind regards,
Jessica