Is there any specific list of things that still has to be done before voice calls are more or less functional for the N900? I looked around the Gitlab but couldn't seem to locate anything. The wiki[0] mentions a requirement of "libcmtspeechdata" but there doesn't seem to be any other information beyond that.

[0] https://wiki.postmarketos.org/wiki/Nokia_N900#Additional_inf...

Yes, I had intended on spending this month on the audio codec for nexus 5 but was deterred by the modem not working. I want to split my time between reverse engineering mediatek baseband and getting a pmos daily driver going with the shelli UI. So hope to come back to the audio codec in about a month. Hopefully somebody comes along and does it before me! :p ;)