Hello @hane_vv. Thanks for posting this question. I asked around and found that we do not currently have plans to add PPP (PPPoS) support to the FreeRTOS TCPIP stack.
I’m not an expert in PPP myself but you might be in luck. It looks like there are several FreeRTOS users over the years who’ve implemented PPP in one form or another (example 1, example 2, example 3). I can’t vouch for how these will work for you. There is also a post on implementing your own, if you’d like.