- Added an HAProxy example in the reverse proxy documentation. Contributed by Benoît S. (“Benpro”). ([\#4541](https://github.com/matrix-org/synapse/issues/4541))
- Transfer bans on room upgrade. ([\#4642](https://github.com/matrix-org/synapse/issues/4642))
- Add configurable room list publishing rules. ([\#4647](https://github.com/matrix-org/synapse/issues/4647))
- Support .well-known delegation when issuing certificates through ACME. ([\#4652](https://github.com/matrix-org/synapse/issues/4652))
- Allow registration and login to be handled by a worker instance. ([\#4666](https://github.com/matrix-org/synapse/issues/4666), [\#4670](https://github.com/matrix-org/synapse/issues/4670), [\#4682](https://github.com/matrix-org/synapse/issues/4682))
- Reduce the overhead of creating outbound federation connections over TLS by caching the TLS client options. ([\#4674](https://github.com/matrix-org/synapse/issues/4674))
- Add prometheus metrics for number of outgoing EDUs, by type. ([\#4695](https://github.com/matrix-org/synapse/issues/4695))
- Return correct error code when inviting a remote user to a room whose homeserver does not support the room version. ([\#4721](https://github.com/matrix-org/synapse/issues/4721))
- Prevent showing rooms to other servers that were set to not federate. ([\#4746](https://github.com/matrix-org/synapse/issues/4746))
Bugfixes
--------
- Fix possible exception when paginating. ([\#4263](https://github.com/matrix-org/synapse/issues/4263))
- The dependency checker now correctly reports a version mismatch for optional
dependencies, instead of reporting the dependency missing. ([\#4450](https://github.com/matrix-org/synapse/issues/4450))
- Set CORS headers on .well-known requests. ([\#4651](https://github.com/matrix-org/synapse/issues/4651))
- Fix kicking guest users on guest access revocation in worker mode. ([\#4667](https://github.com/matrix-org/synapse/issues/4667))
- Fix an issue in the database migration script where the
`e2e_room_keys.is_verified` column wasn't considered as
a boolean. ([\#4680](https://github.com/matrix-org/synapse/issues/4680))
- Fix TaskStopped exceptions in logs when outbound requests time out. ([\#4690](https://github.com/matrix-org/synapse/issues/4690))
- Fix ACME config for python 2. ([\#4717](https://github.com/matrix-org/synapse/issues/4717))
- Fix paginating over federation persisting incorrect state. ([\#4718](https://github.com/matrix-org/synapse/issues/4718))
Internal Changes
----------------
- Run `black` to reformat user directory code. ([\#4635](https://github.com/matrix-org/synapse/issues/4635))
- Reduce number of exceptions we log. ([\#4643](https://github.com/matrix-org/synapse/issues/4643), [\#4668](https://github.com/matrix-org/synapse/issues/4668))
- Introduce upsert batching functionality in the database layer. ([\#4644](https://github.com/matrix-org/synapse/issues/4644))
- Fix various spelling mistakes. ([\#4657](https://github.com/matrix-org/synapse/issues/4657))