Grammar of ～がどうかは問題ない

Question

A textbook I am reading through provided the following explanation of ～を問わず:

～がどうかは問題なく、どれにも同じことが言える。

I understand the basic idea of what this means because I've read English explanations of を問わず but I do not understand the structure of the Japanese explanation and would not have been able to generate it on my own.

1. In the first part, 問題 is the subject of なく and が was omitted because it is such a common expression (as least I think that is true). If that is the case, what is the first が being used for? Why does it not require a verb?

2. Was it necessary to include は after どうか or could it have been understood (in the same was as が and を can often be understood in expressions like ～かどうか知らない and ～かどうか構わない).

Answer 1

First of all, I want to make sure that everyone understands that in both:

「～を問{と}わず」 and

「～がどうかは問題なく、どれにも同じことが言える。」,

the 「～」 part will always be a noun or noun phrase.

Both mean "regardless of (noun)" even though the latter obviously sounds explanatory.

Now, let us pick an actual noun to replace the "～" so that things will hopefully become clearer. The nouns often used in 「～を問わず」 in help-wanted ads, for instance, include 「年齢{ねんれい}」、「経験{けいけん}」、「学歴{がくれき}」, etc.

「年齢を問わずご応募{おうぼ}ください」 = "Please apply regardless of age."

I presume that you have no problem with that phrase.

「年齢を問わず」　means:

「年齢がどうか（＝何歳{なんさい}か）は問題なく、どれ（＝どんな年齢の人）にも同じことが言える」

Hope you are following me so far. That literally means "What the age (of the person) is is no problem, it (= the job applications) can be said about people of all ages."

1. In the first part, 問題 is the subject of なく and が was omitted because it is such a common expression (as least I think that is true). If that is the case, what is the first が being used for? Why does it not require a verb?

I'll be honest; I see serious comprehension problems here.

The subject is not 「問題」; It is 「～がどうか」 and the predicate is 「問題なく」.　Please remember that 「～がどうか」 functions as a noun. 「は」 is, of course, the topic marker.

The 「が」 cannot be omitted because the whole phrase 「～がどうか」 forms a noun phrase. The 「が」 is the subject marker within the little phrase 「～がどうか」 ("how (something) is").

「問題なく」 is the 連用形 of 「問題ない」. You do not need a verb to form a predicate, do you? 「この花は赤い。」 is a perfectly grammatical sentence without a single verb in it.

2. Was it necessary to include は after どうか or could it have been understood (in the same was as が and を can often be understood in expressions like ～かどうか知らない and ～かどうか構わない).

The 「は」 is necessary because this is written Japanese, not informal spoken language.　You should not compare this with 「～かどうか知らない」 or 「～かどうか構わない」 when those are the entire sentences.

The sentence in question is much longer with 「どれにも同じことが言える」 in the second half and the 連用形 in mid-sentence.