There are only two realities: saṅkhāra and asaṅkhāra; All others are paññatti

There are only two realities: saṅkhāra (dependent origination such as aggregate) and asaṅkhāra (no dependent origination such as nibbāna). All others are paññatti (concept;imagine;not reality) because saṅgkhāra must have tree sub-characteristics and asaṅkhāra must have not tree sub-characteristics. But paññatti has nothing, it can't arise like saṅkhāra and can't cease saṅkhāra like nibbāna.
By VN Parivāra of upāli-etadagga:

Aniccā sabbe saṅkhārā, dukkhānattā ca saṅkhatā; Nibbānañceva paññatti, anattā iti nicchayā.
Saṅkhāra, which means saṅkhata(effect-saṅkhāra)*, is anicca&dukkha&anattā; But only nibbāna&paññatti which are explained as only anattā.
(*Saṅkhāra, which means cause-saṅkhāra, use in more fixed meaning word, such as saṅkhāra-khandha, saṅkhāra-paṭiccasamuppāda. You can notice it in each context, because it is already appear clearly.)

And by KN Paṭisambhidāmagga of sāriputta-mahāsāvaka:

sabbe saṅkhārā aniccā sabbe saṅkhārā dukkhā sabbe dhammā anattāti
All saṅkhāra are anicca, all saṅkhāra are dukkha, and all dhammā are anattā.

There is no saṅkhāra which is not aggregates (Khandhavinimuttako hi saṅkhāro nāma natthi.)
Below, the second group is the conclusion of the first group, Sutta. Ma. Mū. Cūḷasaccakasuttaṃ:

"Aggivessana, 2 the Blessed One disciplines his disciples in this way; this part of the Blessed One's instruction is generally presented to his disciples: ('Form is inconstant. Feeling is inconstant. Perception is inconstant. Fabrications are inconstant. Consciousness is inconstant.) Form is not-self. Feeling is not-self. Perception is not-self. Fabrications are not-self. Consciousness is not-self. (All fabrications are inconstant.) All phenomena are not-self.' This, Aggivessana, is the way in which the Blessed One disciplines his disciples; this part of the Blessed One's instruction is generally presented to his disciples."

However, "All phenomena are not-self" in above context include more than "Form is inconstant", because it include more two, nibbāna and paññatti, as I have described above.
Abhidhamma and atthakathā have this same explanation as well.