How would such upload filters work given the presence of lots of Linux machines, where the software is controlled by mere users?

Wouldn't this sort of thing have the effect of banning open source software from general on-the-internet use?

Not just open source.

- Every web app being built.

- google docs

- every ebay post

- Etsy

I mean technically speaking every post, put and patch operation is an upload. It might be JSON (these days) but they are still data being uploaded.

I use Kafka, and the data I upload there is raw binary (formatted through schemas).

This could only be proposed by an idiot.