drupal 11.1.2 support

Why do you believe that to be the case? I am able to install Drupal 11.1.2 and then install Bootstrap5 4.0.3 successfully.

This is the sequence I used -

ddev config --project-type=drupal --php-version=8.3 --docroot=web
ddev composer create 'drupal/recommended-project:^11'
ddev composer require 'drush/drush'
ddev drush site:install
ddev composer require 'drupal/bootstrap5:^4.0'

I did run into an issue when I then tried to create a Bootstrap5 subtheme which I submitted as an issue 🐛 subtheme generation via generate-theme broken Active .

It would probably help to post the errors or description of why you believe there's a support/compatibility issue.