Regardless of whether or not~, it doesn't change the fact that~
Regardless of whether or not only local people are allowed to attend, it does not change the fact that a lot of people are crowded in one place
Regardless of whether attendance is limited to locals or not, it's still a lot of people in one place
Regardless of whether or not~
～しようとしまいと
only local people are allowed to attend
現地の人のみの観戦を許可する
attendance is limited to localsもOKですね。
Regardless of whether or not only local people are allowed to attend,
現地の人のみの観戦を許可しようがしまいが
〜に変わりはない。
it's still~ (まだ〜)
it doesn't change the fact that~ (長くて覚えにくいかもしれませんが、直訳に一番近くてよく使われている表現です。)
一か所に沢山の人が集まることに変わりはない。
it does not change the fact that a lot of people are in one place
it's still a lot of people crowded in one place
英語で「集まる」の直訳の「gather」を使うと通じますが、実は少し不自然ですね。
ご参考になれば幸いです。
アメリカ合衆国 
