This is a regular discussion here to use LetsEncrypt with multiple Traefik instances with Docker Swarm. It's too bad that Docker Swarm configs and secrets are not update-able.
Traefik EE supports "distributed" LetsEncrypt out-of-the-box, it requires a subscription, I think it uses consul as distributed storage.
It was discussed to use a shared folder to store acme.json, not sure if that works, haven't tested myself.
I build a proof-of-concept to use a certbot instance in Docker Swarm behind Traefik that provides a Traefik dynamic configuration via http with certificates inline.
I also build a proof-of-concept to run syncthing as distributed storage in Docker Swarm on which the dynamic config file could be stored - if you prefer provider.file over provider.http. Note that syncthing syncing is probably too slow to use directly with Traefik's acme.json.
If you already have a distributed storage, then adapting my certbot to create the dynamic config file is probably the easiest solution, use it with provider.file and enable watch.