i have a tp-link td-w8961n he isn't supported with openwrt but i want to connect two routers that support openwrt (xiaomi mi 4c) with him (tp-link td-w8961n) using PPPOE, is that possible ?
Can i connect two router with a modem via pppoe protocol?
What would you like to achieve, i.e. why PPPoE and not plain Ethernet?
Be aware that OpenWrt only implements classic CPE VDSL support for lantiq, there is currently no support for the DSLAM side of this, nor master/ slave point-to-point connections.
so it won't work on these devices
If I understood you correctly (for a master-slave point-to-point connection between two td-w8961n), then - no.
At least not without a lot of basic development work on the modem driver code (and it might/ will still require a different modem firmware as well).
But lantiq chips can be DSLAM as well right? Only misses the software?
The hardware is different. A DSLAM transmits data to the customer's DSL modem on high frequencies. The customer's modem hardware transmits back to the DSLAM on low frequencies. Setting up your own DSLAM would require completely different analog filters than are in a customer modem.
…as well as different firmware blobs (whose licensing would be an open question) and probably driver changes.