NetworkManager 1.21.3 Is Another Step Towards NM 1.22
The 1.21.3 release does have a fix for the newly released Intel IWD 1.0 wireless daemon. Aside from that it's mostly been ongoing core code improvements and other related work for this widely-used network management component on the Linux desktop.
Some of the larger changes worked on for the NetworkManager 1.22 release include removing BlueZ 4 support (thus BlueZ 5 is now the base requirement for Bluetooth networking support), a core change that could result in a faster start-up completed state for the systemd service, finishing the removal of WiMAX bits from NetworkManager (WiMAX support itself was dropped back in 2016 from NetworkManager), and other internal improvements.
Those interested in exploring more of the code/changes going into the what will become NetworkManager 1.22 can grab the newest 1.21.3-dev code via the GitHub mirror.