Serviceworker.js 404 not found


I have setup gitlab within a proxmox LXC container using ubuntu 20.04 LTS and apt.
So far i was able to install and setup everything. The only thing, that bugs me is, when i log in i see an empty screen. When i check the developer console in the browser i see that the serviceworker.js could not be loaded and returns with a StatusCode 404 not found.

When i remove servivceworker.js from the domain after i logged in, i can see my repositories and browse gitlab without any issue.

I have a pretty standard gitlab.rb. The only thing i have configured is sending of emails via smtp and the external url.

external_url ''
gitlab_rails['gitlab_email_enabled'] = true
gitlab_rails['gitlab_email_from'] = ''
gitlab_rails['gitlab_email_display_name'] = 'GitLab Admin'
gitlab_rails['gitlab_email_reply_to'] = ''
gitlab_rails['smtp_enable'] = true
gitlab_rails['smtp_address'] = ''
gitlab_rails['smtp_port'] = 25
gitlab_rails['smtp_domain'] = ''
gitlab_rails['smtp_tls'] = false
gitlab_rails['smtp_openssl_verify_mode'] = 'none'
gitlab_rails['smtp_enable_starttls_auto'] = false
gitlab_rails['smtp_ssl'] = false
gitlab_rails['smtp_force_ssl'] = false
gitlab_rails['gitlab_email_subject_suffix'] = '[GitLab]'
gitlab_rails['webhook_timeout'] = 10
gitlab_rails['trusted_proxies'] = [ '', '' ]

Gitlab runs on an SSL port 443 and is setup behind an apache reverse proxy.

the apache config:

<IfModule mod_ssl.c>
 <VirtualHost *:443>
  ProxyPreserveHost On
  ProxyRequests Off

  ProxyPass /
  ProxyPassReverse /

  Header edit Location ^
  RequestHeader set X-Forwarded-Proto "https"

  SSLProxyEngine On
  SSLProxyVerify none
  SSLProxyCheckPeerCN off
  SSLProxyCheckPeerName off
  SSLProxyCheckPeerExpire off

  ErrorLog ${APACHE_LOG_DIR}/git.mydomain.de_error.log
  CustomLog ${APACHE_LOG_DIR}/git.mydomain.de_access.log combined

  Include /etc/letsencrypt/options-ssl-apache.conf
  SSLCertificateFile /etc/letsencrypt/live/
  SSLCertificateKeyFile /etc/letsencrypt/live/

The issue occurs in both cases, when i open the frontend via the internal ip of the LXC container (https://192.168.1.xx:443) or via the reverse proxied domain from external (

Does anybody have an idea what could be wrong?