はどうであれ means "whatever X may be", "regardless of X": the speaker grants that X could be anything and says it changes nothing. It follows a noun, and the second half is a firm judgement, a principle or a decision.
The nouns are abstract ones whose content is open: けっか結果, りゆう理由, じじょう事情, かこ過去, かたち形, ほうほう方法, どうき動機.
が in place of は means the same: けっか結果がどうであれ.
To name two possibilities instead of leaving it open, repeat であれ after each noun: "whether it's X or Y".
であれ is the written form of であっても, and はどうであれ belongs to essays, speeches and serious argument. In conversation, say はどうでもor がどうだろうと.