In what sutta does the Buddha talk about Paccekabuddhas? Question is in the title.
Thank you for your time.
In MN116,

Once upon a time, five hundred Buddhas awakened for themselves dwelt
for a long time on this Isigili. They were seen entering the mountain,
but after entering were seen no more. When people noticed this they
said: ‘That mountain swallows these hermits!’ That’s how it came to be
known as Isigili.
desessāmi, bhikkhave, paccekabuddhānaṁ nāmāni.
I shall teach the names of the Buddhas awakened for themselves.
Taṁ suṇātha, sādhukaṁ manasi karotha, bhāsissāmī”ti. 
Listen and pay close attention, I will speak.
“Yes, sir,” they replied. The Buddha said this:
“The Buddhas awakened for themselves who dwelt for a long time on this
Isigili were named Ariṭṭha, Upariṭṭha, Tagarasikhin, Yasassin,
Sudassana, Piyadassin, Gandhāra, Piṇḍola, Upāsabha, Nītha, Tatha,
Sutavā, and Bhāvitatta. ......
These and other mighty ones awakened for themselves, enders of the
attachment to rebirth— honor these great hermits who are fully
extinguished, having got past all ties, limitless.”

Other translation: From Piyadassi Thera