Ignition Encryption

Does Ignition by default use encryption (e.g., TLS)? Or is the default state a non-encrypted communication since it typically runs in isolated networks?

Your answer is here:

Secure Communication (SSL / TLS) - Ignition User Manual 8.1 - Ignition Documentation (inductiveautomation.com)

Ignition versions 8.0.4 and later default to TLS versions 1.2 and 1.3 with a valid certificate. Older versions of Ignition should be upgraded to offer protection against known vulnerabilities.

The default state is unencrypted--you have to install a certificate to enable encryption.