I don’t use Cloudflare, but if you do, read the specific Subscription Agreement that you think you agree to.
There’s a “Limitation on Serving Non-HTML Content” clause appearing in at least one posted agreement.
Although future Cloudflare R2 will need new terms, I thought the B2 plan uses a content delivery network.
For those seeking to avoid egress fees, I found some discussion on the limits and catches of “free” here.