I created my own filter plugin and did
bundle install under directory of plugin. Also created .gem file, but after this bin/logstash doesn't work because of that problem: "No such file to load -- bundler " in ruby-kernel. OS is clear and logstash too, this is virtual machine. All gems and libraries installed. bin/logstash and bin/logstash-plugin works fine before command execution
In official article there is no words about this and version of ruby ..
Ubuntu 20.04 desktop,