I went down this rathole.
They first grind up the bugs they eat in their mouths, then they have a chamber with bacteria which further reduce their food, then their intestines finish the job.
ETA, since you all are such curious cats:
https://wildlifefaq.com/platypus-stomach/
and
https://platypus.asn.au/platypus-myths/
Sooo, “gullet”?