Issue with routing http flow with Traefik - docker

Question

I have a small lab setup on docker lab server where I have several containers. I wanted to set up a proxy with Traefik, but I stuck on one thing.
Looks like routing works fine but I am having err_connection_refused when I try to access routed services by the browser.
It works fine with the curl command.
Using DNSMasq to manage records - traefik for proxy.
Below docker-compose files for traefik and test container which I am using for testing the proxy.
Heimdall Dashboard:
---
version: "2.1"
services:
heimdall:
image: lscr.io/linuxserver/heimdall:latest
container_name: heimdall
environment:
- PUID=1000
- PGID=1000
- TZ=Europe/London
volumes:
- /path/to/appdata/config:/config
restart: unless-stopped
labels:
- "traefik.http.routers.heimdall-www.rule=Host(`heimdall.lab`)"
- "traefik.http.services.heimdall-www.loadbalancer.server.port=80"
networks:
default:
name: traefik_default
Traefik container:
version: '3'
services:
reverse-proxy:
# The official v2 Traefik docker image
image: traefik:v2.9
# Enables the web UI and tells Traefik to listen to Docker
command: --api.insecure=true --providers.docker
ports:
# The HTTP port
- "80:80"
# The Web UI (enabled by --api.insecure=true)
- "8080:8080"
volumes:
# So that Traefik can listen to the Docker events
- /var/run/docker.sock:/var/run/docker.sock
whoami:
# A container that exposes an API to show its IP address
image: traefik/whoami
labels:
- "traefik.http.routers.whoami.rule=Host(`whoami.lab`)"
- "traefik.http.services.whoami.loadbalancer.server.port=80"
DNSmasq entry
address=/.lab/127.0.0.1
I dont understand why curling works fine e.g.:
curl -H Host:whoami.lab http://192.168.0.150
Hostname: 1ad1e42dd818
IP: 127.0.0.1
IP: 172.21.0.4
RemoteAddr: 172.21.0.2:54128
GET / HTTP/1.1
Host: whoami.lab
User-Agent: curl/7.84.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 192.168.0.100
X-Forwarded-Host: whoami.lab
X-Forwarded-Port: 80
X-Forwarded-Proto: http
X-Forwarded-Server: ca631c80565a
X-Real-Ip: 192.168.0.100