Cannot install Nyquist Band

I cannot activate it in Plug-in manager but it does not appear in effect list (Audacity 2.1.2 in French). If I reopen Plug in manager the plugin is always New.

Even activated dose not appear in effect list?

Where can I get this plug-in to test it?
Why are you using an ancient version of Audacity? (the current version is 2.3.2 and is available via the Audacity website: