Thanks for your assistance @meyay. I made the changes you suggest – I had to add port 443:443 to traefik’s yml after removing the web trees entrypoint (not sure why but traefik dashboard was unreachable until I did this).
I modified webtrees yml per your advice – using label traefik.port=80 I got “bad gateway”, using traefik.http.services.webtrees.loadbalancer.server.port=80 I end up with the ‘bad request’ error I started with.
So back to square one… although it’s very good to know that I don’t need to map ports with docker, traefik does that by itself.
