A local chain here ships soup in some sort of biodegradable coated-cardboard-bucket-thingies. They still put a plastic lid on it, but I wouldn't dismiss cardboard/paper.

They're good enough for transport, though they do degrade pretty fast (they'll get leaky after a day or so).

Most of the time, these are actually done with PFAS ‘wax’ regardless of how it is labeled.

Just like them labeling a container with a plastic lid as ‘biodegradable’.