@AnastasiaD3V
So I've conducted testing on this myself and was able to replicate this.
For me, I have managed to resolve this by downgrading Composer:
Please can you try:
composer self-update 1.10.17
And then run:
composer create-project flarum/flarum . --stability=beta --prefer-dist
To confirm, have added my findings to @luceos's bug report here: composer/composer9396