Vyxal Ṁ, 11 10 bytes

-1 thanks to Neil

ƛkanḟ;∑?LḊ

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Explanation

ƛkanḟ›;∑?LḊ
ƛ            Start a mapping lambda for input
 ka          Lowercase alphabet
   n         Current letter
    ḟ        Find letter in the alphabet, return index
      ;      Close mapping lambda
       ∑     Sum the list of indices.
        ?L   Get Length of input
          Ḋ  Check if Sum is divisible by the length.

Vyxal Ṁ, 11 10 bytes

-1 thanks to Neil

ƛkanḟ;∑?LḊ

Try it Online!

Explanation

ƛkanḟ;∑?LḊ
ƛ            Start a mapping lambda for input
 ka          Lowercase alphabet
   n         Current letter
    ḟ        Find letter in the alphabet, return index
     ;       Close mapping lambda
      ∑      Sum the list of indices.
       ?L    Get Length of input
         Ḋ   Check if Sum is divisible by the length.

Vyxal Ṁ, 11 bytes

ƛkanḟ›;∑?LḊ

Explanation

ƛkanḟ›;∑?LḊ
ƛ            Start a mapping lambda for input
 ka          Lowercase alphabet
   n         Current letter
    ḟ        Find letter in the alphabet, return index
     ›       Increment by 1, because 0-indexed
      ;      Close mapping lambda
       ∑     Sum the list of indices.
        ?L   Get Length of input
          Ḋ  Check if Sum is divisible by the length.

Try it Online!

Vyxal Ṁ, 11 10 bytes

-1 thanks to Neil

ƛkanḟ;∑?LḊ

Try it Online!

Explanation

ƛkanḟ›;∑?LḊ
ƛ            Start a mapping lambda for input
 ka          Lowercase alphabet
   n         Current letter
    ḟ        Find letter in the alphabet, return index
      ;      Close mapping lambda
       ∑     Sum the list of indices.
        ?L   Get Length of input
          Ḋ  Check if Sum is divisible by the length.

Vyxal Ṁ, 11 bytes

ƛkanḟ›;∑?LḊ

Try it Online!

Vyxal Ṁ, 11 bytes

ƛkanḟ›;∑?LḊ

Explanation

ƛkanḟ›;∑?LḊ
ƛ            Start a mapping lambda for input
 ka          Lowercase alphabet
   n         Current letter
    ḟ        Find letter in the alphabet, return index
     ›       Increment by 1, because 0-indexed
      ;      Close mapping lambda
       ∑     Sum the list of indices.
        ?L   Get Length of input
          Ḋ  Check if Sum is divisible by the length.

Try it Online!