Mounting volume on docker-compose, but nginx container sees empty directory - docker

Question

I want to run nginx with docker-compose.
docker-compose.yml:
version: "3.9"
services:
custom-nginx:
image: custom-nginx:latest
network_mode: host
volumes:
- /etc/letsencrypt:/etc/letsencrypt:ro
ports:
- 80:80
- 443:443
restart: always
nginx:
depends_on:
- custom-nginx
image: nginx:alpine
volumes:
- /etc/letsencrypt:/etc/letsencrypt:ro
restart: always
The folder gets mounted but when I look into it from the nginx container it's empty:
/ # ls -al /etc/letsencrypt/
total 4
drwxr-xr-x 2 root root 40 Nov 21 18:00 .
drwxr-xr-x 1 root root 4096 Nov 21 20:07 ..
The custom-nginx Dockerfile is just
FROM nginx:alpine
COPY nginx.conf /etc/nginx/nginx.conf
I assume it has to do with my permissions maybe?
ls -l /etc | grep lets
drwxr-x--- 9 root docker 4096 Nov 21 17:43 letsencrypt
The docker group has rx on the folder recursively. The docker user on the host can see all those folders, and the docker user is running docker in rootless mode.
I was assuming that the root user of the container should see all files the same way as the docker user on the host machine?
What am I missing here?
EDIT: This is the content of /etc/letsencrypt on the host
ls -l /etc/letsencrypt/
total 32
drwx------ 3 root root 4096 Nov 21 17:32 accounts
drwxr-x--- 3 root docker 4096 Nov 21 17:43 archive
-rwx------ 1 root root 207 Nov 12 2021 cli.ini
drwx------ 2 root root 4096 Nov 21 17:43 csr
drwx------ 2 root root 4096 Nov 21 17:43 keys
drwxr-x--- 3 root docker 4096 Nov 21 17:43 live
drwx------ 2 root root 4096 Nov 21 17:43 renewal
drwx------ 5 root root 4096 Nov 21 17:32 renewal-hooks
The container, inside its nginx.conf, only references /etc/letsencrypt/live/<domain_name>fullchain.pem which actually is a link:
/etc/letsencrypt/live/<domain_name>/fullchain.pem -> ../../archive/<domain_name>/fullchain1.pem
But both live and archive folders seem to have the necessary permissions in my opinion...