How to enable to send all istio-proxy application logs (not access logs) into file?

Config
1

Install istio into local docker-desktop k8s
istioctl install --set profile=demo -y
edit istio-ingressgateway deployment to write all logs (except accesslogs) into file /etc/istio/proxy/app.log:
- args:
- --log_target=/etc/istio/proxy/app.log
after restarting pods in /etc/istio/proxy/app.log exists only few messages, instead of all logs, that appears in stdout.

Also if trace or debug level for envoy components enabled these logs don’t appear in /etc/istio/proxy/app.log

2

Here: Setting --log_target argument in istio-ingressgateway doesn't send all logs into file · Issue #36193 · istio/istio · GitHub
John Howard said that it works as designed:

This is working as intended, those log settings apply only to istio-agent, not envoy logs which are configured separately.

So the question is how to write envoy’s logs (not access logs) into file?