The problem

intl/icu causes problems when using Microsoft Azure (source)

Enabling the PHP intl Extension

This is the tricky part of the guide! At the time of writing this cookbook,
Microsoft Azure Website provided the intl extension, but it's not enabled by
default.

intl/icu causes problems when using Heroku (source)

One of Symfony’s dependencies, symfony/icu, requires the intl PHP extension,
but doesn’t list it as a dependency. This will prevent a deploy, and lead to
confusing error messages about a package named lib-icu missing from the system.

intl/icu causes problems in Symfony trainings

I can confirm that whenever we deliver a Symfony training, one or more people
suffer the intl/icu problems when trying to install or use Symfony.

The solution

I'm aware of the "ICU and Deployment Problems" section that you can read in
the Intl component doc, but I think that we could do more.

Can anyone think of a better solution to use the intl extension when available
but to not bother people when is not available?