Kanboard behind traefik with 'path'

I do succeed to run kanboard in docker as a single webapp on an URL,
but now, I need to make it works behind a traefik which will deploy many apps.

As I can’t play with sub-domains like http://kanboard.server.lan
I need to map it on http://server.lan/kanboard

I’ve tried things with docker-compose, the most working thing I get is a 302 redirect " location /login"
How to tell kanboard his “root” is /kanboard ?

Failed to use "define(‘KANBOARD_URL’…) in config.php
Failed to use the setting in admin > settings > app url


Did you manage to find an answer to this, i’m getting this also. It looks like some web apps do not handle relative paths via reverse proxy well. If you tried this with an apache container, this would work as expected.

I tried something on this thread with no luck.