None of these flags exist in current Synapse:

- msc3266_enabled: MSC3266 support was stabilized in Synapse v1.153.0 and the room summary API is now always enabled

- msc4140_enabled: this was never a Synapse configuration setting in any released version. Delayed events have always been controlled by the `max_event_delay_duration` setting, which the playbook was emitting alongside the flag. The toggle is now named `matrix_synapse_delayed_events_enabled`.

- msc4429_enabled: MSC4429 support has not landed in any released Synapse version, so this flag never had any effect

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>