I wanted to have all the services connected thru SSL. It was fairly easy for apache sites. But I wasn't able to make it work with ReverseProxy for Docker containers. Until now.

Thanks to excellent tutorial for RocketChat. I was able to make a new template for my Apache configuration. And for all of you that have similar problem I posting it here.

<VirtualHost *:80>
    ServerName DOMAIN
    ServerAlias www.DOMAIN
    RewriteEngine on
    RewriteCond %{SERVER_NAME} =www.DOMAIN [OR]
    RewriteCond %{SERVER_NAME} =DOMAIN
    RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,QSA,R=permanent]
</VirtualHost>

<VirtualHost *:443>
    ServerAdmin EMAIL
    ServerName DOMAIN
    ErrorLog /home/UUSER/error.log
    TransferLog /home/UUSER/access.log
    AssignUserId UUSER UUSER
    LogLevel info
    SSLEngine On
    SSLCertificateFile /etc/letsencrypt/live/DOMAIN/cert.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/DOMAIN/privkey.pem
    SSLCertificateChainFile /etc/letsencrypt/live/DOMAIN/chain.pem

    <Location />
            Order allow,deny
            Allow from all
    </Location>

    RewriteEngine On
    RewriteCond %{HTTP:Upgrade} =websocket [NC]
    RewriteRule /(.*)           ws://localhost:DPORT/$1 [P,L]
    RewriteCond %{HTTP:Upgrade} !=websocket [NC]
    RewriteRule /(.*)           http://localhost:DPORT/$1 [P,L]

    ProxyPassReverse / http://localhost:DPORT/
</VirtualHost>

Just change EMAIL, DOMAIN, UUSER, DPORT.

Before enabling the site do:

certbot certonly --webroot -w /var/www/html -d DOMAIN

Then enable the site and everything should work.