I have to admit I was a bit lazy and started with a new vm when setting up my instance earlier today but I found this thread in the traefik community where someone was asking question on how to setup their traefik config for Lemmy. It's a bit old, last post is from spring of 2020 but it's already traefik v2, so hopefully not much changed since then...
https://community.traefik.io/t/issues-with-router-priorities/4565/12
EDIT: By being lazy and starting with a new VM, I meant that I could just use the Ansible playbook and had it running in a few minutes.