kzyyy if you could do me a favor ?
Edit the following file:
vendor/league/flysystem/src/Adapter/Local.php
and add after line 148:
$location = $this->applyPathPrefix($path);
$this->ensureDirectory(dirname($location));
// Add the following:
var_dump($location, $path); exit;
// That's it..
$stream = fopen($location, 'w+b');
Run another upload and check the debug pane (or your xhr call in the browser inspection panel, in chrome : F11 and network).
Post what you find out, then delete the vendor directory and run another
composer install --prefer-dist --no-dev
