indubitably vs beyond doubt

indubitably is not an adjective while beyond doubt is an adjective.

Word	Noun	Adjective	Verb	Adverb
indubitably	No	No	No	Yes
beyond doubt	No	Yes	No	Yes

As adverbs, indubitably and beyond doubt are synonyms defined as:

indubitably and beyond doubt: in a manner or to a degree that could not be doubted

Other synonyms of indubitably include beyond a doubt, beyond a shadow of a doubt.

indubitably (adjective)	beyond doubt (adjective)
	too obvious to be doubted

indubitably (adverb)	beyond doubt (adverb)
in a manner or to a degree that could not be doubted	in a manner or to a degree that could not be doubted