For Apache running in a docker container: How to install an Intermediate/chain certificate to link it to a trusted root certificate

I followed Missing Intermediate/chain certificate - Apache - How to correct?

I'm using Bitnami's images running in a docker container on Ubuntu Server. The section of docker-compose.yml regarding Apache is:

  apache:
    restart: unless-stopped
    container_name: apache
    image: bitnami/apache:latest
    environment:
      - APACHE_HTTP_PORT_NUMBER=8080 
      - APACHE_HTTPS_PORT_NUMBER=8443
    ports:
      - 80:8080
      - 443:8443
    volumes:
      - ./apache_data:/app
      - ./apache-certs:/certs
      - .my_vhost.conf:/vhosts/my_vhost.conf:ro
 

I'm using a sub domain (slimzulu.hopto.org) registered with No-IP I also paid for a TrustCor Premium DV SSL certificate, downloaded the PEM file and PEM Chain file. I renamed my slimzulu.hopto.org.key to server.key and the downloaded slimzulu.hopto.org.pem to server.crt and copied both to my /home/nols/www/apache-certs directory.

I get a warning from the broser when I access my home page with https://slimzulu.hopto.org When I use the SSLShopper service to check my SSL implementation, the result is:

The certificate is not trusted in all web browsers. You may need to install an Intermediate/chain certificate to link it to a trusted root certificate. Learn more about this error. The fastest way to fix this problem is to contact your SSL provider.

I tried to solve the problem by renaming the downloaded slimzulu_hopto_org.pem-chain file to server.pem-chain and copied it to my mapped apache-certs folder but the problem remains.

Any recommedation how to implement the pem-chain file?

Regards,

Nols Smit