How to make an alphabetical guide to taxonomy?

Question

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An attribute is also a taxonomy. It would not be easy to deduce everything in alphabetical order, but so that first the letter itself was at the top, and below it all the terms for this letter, then the same with everyone.
Please provide a code example or a link to one.
Just not plugins.

Answer 1

Collect an array of all taxonomies into one array, which we need to sort into an associative array, where the key will be the first letter of the name of these terms, and the value will be an array of these taxonomies.
Then the array is filtered by keys alphabetically and output.
Maybe it could be better, but I haven't thought of it yet.