This is a sip client using the 2 FXS ports available on routers based on the Infineon Danube (lantiq xway) and running openwrt.
Based on the midge package oem-voip and sofia-sip.
See the INSTRUCTIONS for instructions.
Precompiled binaries for attitude adjustment, barrier breaker and chaos calmer are available here, binaries for openwrt 19.07.2 and 23.05.4 are available as github releases.
Beware openwrt 23.05.4 is too big for this device and it won't be possible to install these packages and their dependencies in a stock image, so you either have to extend the writable partition (I never tried) or build a custom image with many things removed (I provide one for testing in the release but it may not fit your needs, see the workflow for details).
Also, with openwrt 23.05.4 make sure to use the sofia-sip package provided here, the one from the telephony feed has been compiled with stun disabled.
With openwrt 24.10 I couldn't find a way to build an image including sofia-sip/svd/luci-app-svd, the only option is extroot, and even then it's impossible to install the packages required for extroot on the stock image, hence in the workflow I create a stripped down image with the packages for extroot included.