Flarum v1.6.1 has been released as a patch release.
To address a JavaScript compilation problem, causing the mentioning dropdown to hide users, we have published a new v1.6.1 patch release. Please upgrade to v1.6.1, especially if you encounter any issues with your recently upgraded Flarum v1.6.0 community. New installations and upgrades to v1.6.0 will automatically pick up the latest version. For further support use our Support tag on discuss: https://discuss.flarum.org/t/support
You can easily upgrade by using the same upgrade instructions from the v1.6.0 release:
composer update --prefer-dist --no-plugins --no-dev -a --with-all-dependencies
php flarum migrate
php flarum cache:clear
See the upgrade guide documentation for in-depth instructions: https://docs.flarum.org/update#general-steps