Thank you very much.
Replacing the code from Github with the release version did it!
Thanks.
P.S. you might want to update the post: Install Invoice Ninja v5.5 on Ubuntu 22.04
to reflect the suggestion from David:
I’m not sure what is going on, but is looks like you are injecting the vhost config direct into the main conf file.
Best practice would be to setup a vhost file in
/etc/nginx/sites-available/ninja.conf