The phrase "are indisputably" is correct and usable in written English.
It can be used to assert that something is undeniably true or accepted without question.
Example: "The results of the study are indisputably significant, demonstrating a clear correlation between the variables."
Alternatives: "are undeniably" or "are unquestionably."
Dictionary
are indisputably
adverb
In a manner that is incapable of being disputed or argued against.
Exact(60)
The stakes are indisputably high.
The opportunities are, indisputably, immense.
Drugs are indisputably present in Ossining.
These two are indisputably the winners.
Animal welfare campaigners argue industrial farming methods are indisputably cruel.
The Nets are indisputably talented, but they do not inspire fear or dread.
Yet the giant viruses have longer genomes than some bacteria, which are indisputably alive.
Daytime talk shows are indisputably an embarrassment, but are they actually doing anyone any harm?
The principles, the patience, the style laid down in the boys' adolescence are indisputably bearing fruits.
As polarizing as the so-called Miami Thrice have become, they are indisputably compelling.
But if some courses are indisputably better than others, then inevitably, some are worse.
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Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.

Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com