What's the plural form of ultraleftism? Here's the word you're looking for.
Answer
The noun ultraleftism can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be ultraleftism.
However, in more specific contexts, the plural form can also be ultraleftisms e.g. in reference to various types of ultraleftisms
or a collection of ultraleftisms.