No way.

Wiktionary defines "the Establishment" as the ruling class or authority group in society; especially, an entrenched authority dedicated to preserving the status quo.

Arguably, before Donald Trump became president he was part of the Establishment because he was a billionaire. Therefore he wielded a lot of authority. But during his election campaign it became clear that in some way he was also outside of the Establishment and especially not part of the Republican party's inner circle.

But then he won the election and became the president of the United States. It would, in my mind, be absurd to not consider the president of the United States part of the Establishment. Therefore Donald Trump is now part of the Establishment. But his supporters have not abandoned him so how could they ever be anti-Establishment?

Communists dream of a revolution. In the revolution, the Establishment will be replaced with a new Socialist one. They are against the Establishment. But they can only be against the Establishment as long as they keep failing because if they succeed, the Communists themselves become part of the Establishment.

Perhaps the only true anti-Establishment ideology is Anarchism. Anarchists want a revolution like the Communists, but unlike them, they do not want to replace the Establishment with a new one. I don't see how it could ever work out in practice, but Anarchists believe it will.

However, I think that Donald Trump, UKIP and a lot of other political groups can be characterized by something else. Namely the black-and-white world view. Either you are against us or you are with us. They believe that most of the establishment consists of persons who are enemies. But that is orthogonal to being against the establishment itself.

No way.

Wiktionary defines "the Establishment" as the ruling class or authority group in society; especially, an entrenched authority dedicated to preserving the status quo.

Given that definition, Donald Trump was part of the establishment before he became president. But during his election campaign it became clear that in some way he was also outside of the Establishment and especially not part of the Republican party's inner circle.

But then he won the election and became the president of the United States. It would, in my mind, be absurd to not consider the president of the United States part of the Establishment. Therefore Donald Trump is now part of the Establishment. But his supporters have not abandoned him so how could they ever be anti-Establishment?

What it comes down to is are you against Establishment itself, the structure of the Establishment or the people that the Establishment consists of?

Anarchists are against the Establishment itself. They want to reshape society so that it will work without any "ruling class or authority group" at all.

Communists, Fascists and Nazis are against the structure of the Establishment. They seek to change how the Establishment works. Communists want to create a Socialist society while Fascists and Nazis want to create a Fascist state. In these societies, their preferred ideology would dominate.

Neither Donald Trump, UKIP nor any other group you mention, want to change the structure of the Establishment. On the contrary, most of those groups are conservative and want to preserve the status quo. What unites them is the identification of enemies. Trump declared Clinton and Obama the enemies, and UKIP the EU. Those were and are part of the Establishment, but not the Establishment itself.

In my opinion, is not enough for someone to want to oust the current run of incumbents to be anti-Establishment. Because then anti-Establishment would merely be synonymous with populism.