this conf is working for me with iDempiere 9 and Apache
<VirtualHost *:443>
RequestHeader set X_FORWARDED_PROTO 'https' env=HTTPS
ServerName
xxx.yyy.sk DocumentRoot /var/www/html
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
SSLCertificateFile /etc/letsencrypt/live/
yyy.xxx.sk/cert.pem SSLCertificateKeyFile /etc/letsencrypt/live/
yyy.xxx.sk/privkey.pem Include /etc/letsencrypt/options-ssl-apache.conf
SSLCertificateChainFile /etc/letsencrypt/live/
yyy.xxx.sk/chain.pem RewriteEngine On
# websocket
RewriteCond %{HTTP:Upgrade} =websocket [NC]
RewriteRule ^/webui/serverpush/(.*) ws://localhost:8080/webui/serverpush/$1 [P,L]
ProxyRequests Off
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
RequestHeader set "X-Forwarded-Proto" expr=%{REQUEST_SCHEME}
RequestHeader set "X-Forwarded-SSL" expr=%{HTTPS}
ProxyPass /server-status
http://localhost/server-status ProxyPass /webui
http://localhost:8080/webui retry=1 acquire=3000 timeout=600 Keepalive=On
ProxyPass /
http://localhost:8080/webui retry=1 acquire=3000 timeout=600 Keepalive=On
ProxyPreserveHost On
</VirtualHost>