How to open the AVD manager on Ubuntu Linux from the command line?
./android avd is deprecated use ~/Android/Sdk/tools/bin/avdmanager --help instead!
or if it is easier for you, move to the directory and use it like in the old version:
cd ~/Android/Sdk/tools/bin/
./avdmanager
check new [options] with --help or -h before you use avdmanager
first occurence in Android Studio 2.3 !