Local Diagrams.net / draw.io instance with gitlab on-prem

I’ve tried to use diagrams.net / draw.io as docker container on the same machine as my gitlab instance. I followed this instruction. The problem is that gitlab itself already uses port 8080, so I used

docker run -it --rm --name="draw" -p 8084:8084 -p 8443:8443 jgraph/drawio

to run the container on port 8084. The log output seems a little weird, because every port that is mentioned is 8080, e.g.:

window.DRAWIO_BASE_URL = 'http://localhost:8080';

With lsof -i:8084 I can see that this specific container uses the right port:

docker-pr 406538 root    4u  IPv4 4608148      0t0  TCP *:8084 (LISTEN)
docker-pr 406546 root    4u  IPv6 4609027      0t0  TCP *:8084 (LISTEN)

docker ps output:

CONTAINER ID   IMAGE               COMMAND                  CREATED         STATUS         PORTS                                                                                            NAMES
698745f466fb   jgraph/drawio       "/docker-entrypoint.…"   3 minutes ago   Up 3 minutes>8084/tcp, :::8084->8084/tcp, 8080/tcp,>8443/tcp, :::8443->8443/tcp   draw

But when I try to access, like described here via http://localhost:8084/?offline=1&https=0 it doesn’t work at all.

Where is my mistake? Any help appreciated.
Did anyone already successfully host the drawio container on the same machine like gitlab?

My environment:
OS: rockyLinux 8
Gitlab version 16.4