The correct invocation is poetry run synapse_homeserver -c [your homeserver.yaml] (or substitute synapse_homeserver with synapse_worker for workers), however this does not seem to be documented anywhere apart from the [tool.poetry.scripts] section of pyproject.toml. This makes it more difficult for newcomers to Synapse to figure out how to run it after setting it up, so I think those entrypoints should be mentioned somewhere in Synapse's documentation.