"Sylius was not able to figure out the current cart" error

Just switch to needed channel in Symfony Debug Toolbar.

Cannot add product to cart, indefined index

You should in Admin pages add to your first shipping method amount for new channel, it should not be null.

Cannot install sylius/locale

run composer require sylius/locale ^v1.0.0-beta.1

symfony+aimeos+extadm: infinite "loading..."

Can be fixed by adding in your php.ini string: always_populate_raw_post_data = -1


Got from https://aimeos.org/help/help-f15/installed-aimeos-with-laravel-screen-stuck-at-expert-mode-t721.html