Seems the fix was appropriately setting the labels. QBittorrent is still having issues, so I'll move that conversation elsewhere, but this example works fine for Nzbget.
labels:
- "traefik.enable=true"
# NZBGET labels
- "traefik.http.routers.nzbget.entrypoints=http"
- "traefik.http.routers.nzbget.rule=Host(`nzbget.example.com`)"
- "traefik.http.middlewares.nzbget-https-redirect.redirectscheme.scheme=https"
- "traefik.http.routers.nzbget.middlewares=nzbget-https-redirect"
- "traefik.http.routers.nzbget-secure.entrypoints=https"
- "traefik.http.routers.nzbget-secure.rule=Host(`nzbget.example.com`)"
- "traefik.http.routers.nzbget-secure.tls=true"
- "traefik.http.routers.nzbget-secure.tls.certresolver=cloudflare"
- "traefik.http.routers.nzbget-secure.service=nzbget-svc"
- "traefik.http.services.nzbget-svc.loadbalancer.server.port=6789"
- "traefik.docker.network=traefik_network"