There has been over 5682 commits since 2.15 (This will be the last 2.x release (10 years after the first commit was produced for making gerrit 2.x):
* 2.16 release notes https://www.gerritcodereview.com/2.16.html
* 2.16.1 release notes https://www.gerritcodereview.com/2.16.html#2161
* 2.16.2 release notes https://www.gerritcodereview.com/2.16.html#2162
* 2.16.3 release notes https://www.gerritcodereview.com/2.16.html#2163
* 2.16.4 release notes https://www.gerritcodereview.com/2.16.html#2164
* 2.16.5 release notes https://www.gerritcodereview.com/2.16.html#2165
* 2.16.6 release notes https://www.gerritcodereview.com/2.16.html#2166
* 2.16.7 release notes https://www.gerritcodereview.com/2.16.html#2167
* 2.16.8 release notes https://www.gerritcodereview.com/2.16.html#2168
Notable changes:
* **GWTUI**: GWTUI has been deprecated and will be removed in 3.0 (has been done already).
* **PolyGerrit**: A new theme called "dark mode" has been added and can be configured through /settings/.
* **PolyGerrit**: PolyGerrit is now the Default UI.
* **PolyGerrit**: Support added for inline editing (like GWTUI).
* **PolyGerrit**: Support added for project dashboards (like GWTUI).
* Everything has been migrated to NoteDB (Groups, and some minor tables) (Possibly resolving T176532 as we can migrate it to use h2 seeing as only one table is left).
* **its-base**: Repo owners can now get GerritBot to add specific comments or projects or rules. You edit refs/meta/config branch of the repo.
** You create a actions-its-phabricator.config file.
** Following i presume https://github.com/wikimedia/puppet/blob/production/modules/gerrit/files/homedir/review_site/etc/its/actions.config format See https://github.com/GerritCodeReview/plugins_its-base/commit/f3ee7e0796bdee9f2a4868417b933712aa7b7d41