Hi Thomas,
thank you for your kind help.

I'm not sure, due to my lack of knowledge, how I can check if the path from port 443 to port 8080 works in my app when accessed directly on my system.

(base) marco@pc01:~$ sudo netstat -plnt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 19569/nginx: master
tcp 0 0 0.0.0.0:81 0.0.0.0:* LISTEN 19569/nginx: master
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 754/systemd-resolve
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1230/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1035/cupsd
tcp 0 0 0.0.0.0:3000 0.0.0.0:* LISTEN 19569/nginx: master
tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN 1321/postgres
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 19569/nginx: master
tcp 0 0 127.0.0.1:33917 0.0.0.0:* LISTEN 1227/containerd
tcp6 0 0 :::80 :::* LISTEN 19569/nginx: master
tcp6 0 0 :::22 :::* LISTEN 1230/sshd
tcp6 0 0 ::1:631 :::* LISTEN 1035/cupsd

ports 80 and 443 seem both listening and owned by nginx.

How can I check if the backend has the capacity to handle the requested path?