How should I run a multicontainer app/platform with nginx behind traefik?
Although I agree with @BruceBecker's comment, i.e. running two different rproxies, it is possible to run traefik in front of nginx. At the previous job we configured several servers that were running on nginx behind traefik.

Ensure that each microservice has the correct labels. Note that Traefik 2.0 changed significantly.