Bookstack Nginx Proxy Manager HAOS

Hello community, I don’t have a fixed IP. So I use a vps with Nginx Proxy Manager and a domain name. Zerotier makes the link with the vps.

It works perfectly for:
My home assistant (
Tasmoadmin (
And other services that are not on my barmetal HAOS server.

This does not work for Bookstack which is an official addon on HAOS. Despite the https address, it mentions that it is not secure. And the page is completely distorted.

Obviously, Bookstack works perfectly locally or via Zerotier.

I found some answers on reddit, but I don’t understand…