The term Dukkha is a characteristic of everything apart from Nibbana. Refer to The Sabba Sutta;
“Monks, I will teach you the All. Listen & pay close attention. I will speak.”
“As you say, lord,” the monks responded.
The Blessed One said, “What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All. [1] Anyone who would say, ‘Repudiating this All, I will describe another,’ if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range.”
And compare the definition of Everything/All from The Sabba Sutta to ie The Cula-Rahulovada Sutta;
the Blessed One said to him, “What do you think, Rahula — is the eye constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — are forms constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — is consciousness at the eye constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — is contact at the eye constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — whatever there is that arises in dependence on contact at the eye as a mode of feeling, a mode of perception, a mode of fabrication, or a mode of consciousness:[1] Is it constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think, Rahula — is the ear constant or inconstant?”
“Inconstant, lord” …
“What do you think, Rahula — is the nose constant or inconstant?”
“Inconstant, lord” …
“What do you think, Rahula — is the tongue constant or inconstant?”
“Inconstant, lord” …
“What do you think, Rahula — is the body constant or inconstant?”
“Inconstant, lord” …
“What do you think, Rahula — is the intellect constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — are ideas constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — is consciousness at the intellect constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — is contact at the intellect constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
“What do you think — whatever there is that arises in dependence on contact at the intellect as a mode of feeling, a mode of perception, a mode of fabrication, or a mode of consciousness: Is it constant or inconstant?”
“Inconstant, lord.”
“And is that which is inconstant easeful or stressful?”
“Stressful, lord.”
“And is it fitting to regard what is inconstant, stressful, subject to change as: ‘This is mine. This is my self. This is what I am’?”
“No, lord.”
Everything apart from Nibbana is Sankhara, every Sankhara has the characteristic of Dukkha, Anicca and Anatta.