- Add support for [MSC3202](https://github.com/matrix-org/matrix-doc/pull/3202): sending one-time key counts and fallback key usage states to Application Services. ([\#11617](https://github.com/matrix-org/synapse/issues/11617))
- Improve the preview that is produced when generating URL previews for some web pages. Contributed by @AndrewRyanChama. ([\#11985](https://github.com/matrix-org/synapse/issues/11985))
- Improve the generated URL previews for some web pages. Contributed by @AndrewRyanChama. ([\#11985](https://github.com/matrix-org/synapse/issues/11985))
- Track cache invalidations in Prometheus metrics, as already happens for cache eviction based on size or time. ([\#12000](https://github.com/matrix-org/synapse/issues/12000))
- Implement experimental support for [MSC3720](https://github.com/matrix-org/matrix-doc/pull/3720) (account status endpoints). ([\#12001](https://github.com/matrix-org/synapse/issues/12001), [\#12067](https://github.com/matrix-org/synapse/issues/12067))
- Enable modules to set a custom display name when registering a user. ([\#12009](https://github.com/matrix-org/synapse/issues/12009))
