Prefect 2.6.3, Python 3.8. Backend is Prefect Cloud. Code is pretty simple:

import asyncio
from prefect.client.orion import get_client
client = get_client()
resp = asyncio.run(client.read_flow_runs())

But there seems to be a missing argument to cloudpickle in the internal utils (see screenshot) FWIW

prefect flow-run ls

works fine from the command line, so I don't think it's an issue with the api endpoint itself.

Also, many other endpoints do work, for example

client.api_healthcheck()
client.read_deployments()
client.read_block_documents()
client.read_logs()

all seem to work correctly