The systemd 249-rc2 release is primarily made up of fixes compared to the prior release candidate. One new feature though to systemd 249-rc2 is the "ConditionOSRelease" directive.
The ConditionOSRelease directive can be used for matching to a value or relative comparison against key-value pairs found in the /etc/os-release file such as if wanting to ensure a systemd unit file is only used if matching a given value or greater than a defined value.
Systemd 249-rc2 has some backwards-incompatible changes around its net_id built-in of udev, but those alterations primarily affect s390 hardware.
Systemd 249-rc2 is available for download from GitHub . Systemd 249 stable should be out soon and with plenty of time for getting it into the autumn 2021 Linux distribution releases.