Hi,
I could successfully test and use Cloudflare R2 for both uploads and backups. Detailed post here Cloudflare R2: Navigating Setup and Handling Configuration Errors - #40 by kamaljain
Would request to kindly test at your end and review the “Works with Discourse” to Yes for Cloudflare R2. Infact its easier than S3 and more economical, free if <10gb of storage.