these commands was helpful for me on ubuntu 20.4:
sudo service influxdb stop
sudo apt remove influxdb
sudo apt remove influxdb-client
sudo apt remove influxdb2
sudo apt autoclean && sudo apt autoremove
sudo rm -rf /var/lib/influxdb/
sudo rm -rf /var/log/influxdb/
sudo rm -rf /etc/influxdb/
sudo rm -rf ~/.influxdbv2/configs
