This image contains the Signal app pre-installed. Signal enforces strict security rules that block network access if it detects SSL inspection (MitM). To ensure Signal functions correctly when WebFilter is enabled, you must add these domains to the SSL Bypass Domains list in your WebFilter configuration: (Notice the preceding dot (.) that ensures all subdomains are also bypassed)

.signal.org
.signal.art
.signal.tube
.signal.group
.signal.link
.signal.me

Environment Variables

APP_ARGS - Additional arguments to pass to the application when launched.