Tim – I did some testing and empty alt tag sort of affects screenreaders. Empty Alt tag only removes the what the name of the button, but the screen reader still announces that there is a clickable button on the page. If it’s disabled, the screen reader will announce “clickable button unavailable”.
The “clickable button” is somehow taken from a role attribute, but I cannot determine how that could be removed from an individual element or set a class for a role to not announce the button.
The only, and maybe easiest way to remove it from the screen reader is to set it initially hidden. This removes it from both tab order and from being visible by a screen reader. I tried looking at aria-hidden to see if that worked to hide it from the reader, but unfortunately, it hid it entirely.