You need to set the runtime setting
The first one in the list here: https://docs.mendix.com/refguide/custom-settings#general
For the docker buildpack that is done via an environment variable set like:
to environment variables on Docker didn’t work initially.
It turns out it only worked on the first run or when database is not setup. On each docker run configuration passed to it does not get updated on the database. ApplicationUrl eventually got stored in database in table. So, passing the variable to ECS didn’t help. I only noticed the issue when I tried the same with local docker-compose.
Only after changing ApplicationUrl, directly on the database the issue was fixed.