Still based on the Ubuntu 16.04 LTS (Xenial Xerus) operating system series, the Ubuntu Touch OTA-21 update is yet another bugfix release that fixes various issues reported by users from previous OTA updates.
For example, it fixes support for setting up a Google account, it fixes microphone access in the default web browser, and fixes a weird animation issue in Clock app’s timer mode that occurred when the clock hands were moved across the 12-hour clock position.