Laravel Filament's Media Library plugin use Livewire's upload file javascript to send your file to your cloud disk.
When using Cloudflare R2, you will probably get a CORS error and the upload will get canceled.
In your R2 bucket settings, make sure you update the CORS settings like this :
[
{
"AllowedOrigins": [
"https://yourdomain.com"
],
"AllowedMethods": [
"GET",
"POST",
"PUT"
],
"AllowedHeaders": [
"*"
]
}
]
Save and retry :)