checkboxes – Submit button placement on a form with long columns

This question is related to the Sticky submit button at the top and bottom of the form?, and Submit button on top of the long form but I consider has other nuances.

I have a form that is made only with checkboxes. They don’t need to be all checked. I have some javascript to handle possible errors.

This is what can be seen on a standard monitor:

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And this is the complete form:

enter image description here

At the top of each column, I have a button that allows the user to check or uncheck all, so the user can just uncheck all items and send the form without the need to scroll down to the bottom.

I thought the most convenient solution would be to place the submit button at the top of the form so as not to confuse the user if they don’t need to scroll to the end.

Is this a reasonable approach? Are there any reasons why it wouldn’t be?