I know -ly is, but I don't know about -y.
It may be a suffix. For example in gloom-y, stead-y or hand-y.
No, "Y" is not a suffix. It is often used as a letter in words but does not function as a suffix.
The suffix of "hungry" is "-y."
The suffix for tardy is -y.
The suffix of theory is -y.
The suffix of "ready" is "-y".
The suffix for witty is -y.
The suffix of "heavy" is -y.
The suffix of "ready" is "-y".
The suffix of "mercy" is "-y."
The suffix for baby is "-y."
The suffix for witty is -y.
The suffix of "ready" is "-y."
The suffix for tardy is -y.
The suffix of theory is -y.
The suffix of "hungry" is "-y."
The suffix of "merry" is "-y."
The suffix for controversy is "-y," as in "controversy."
The suffix for healthy is "-y".