〜を問わず
regardless of, whether … or
Noun + を問わず
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を問わず means a factor makes no difference: 年齢を問わず、誰でも参加できます, "anyone can take part, regardless of age". 問う means "to ask" or "to question", so it's "without asking about".
It usually follows a noun that implies a range of values: 年齢 (age), 国籍 (nationality), 季節 (season), or pairs of opposites: 男女 (men and women), 昼夜 (day and night), 経験の有無 (with or without experience).
It's common in job adverts, event notices and rules. The meaning is very close to にかかわらず, which also works after whole clauses (するかしないか).
Compare によって, "depending on", which is the opposite: the factor does make a difference.
Examples
年齢を問わず、誰でも参加できます。
Anyone can take part, regardless of age.
男女を問わず、応募できます。
Both men and women can apply.
経験の有無を問わず、歓迎します。
Everyone is welcome, with or without experience.
この公園は季節を問わず、楽しめる。
You can enjoy this park in any season.
国籍を問わず、多くの人が働いている。
Many people of every nationality work here.