Try to find at least something without narrowing the search by "pic32". Or specify "MIPS" instead, as an attempt.
My personal experience - none of open source DSP implementations I met were suitable for real serious project without massive modifications or they were non-suitable at all.
While VAD could be implemented quite easy, under "Echo Cancellation" banner there are plenty of very different algorithms - some of them should work together, selection of others depends on application specifics.
EC stuff is very labor consuming. There are some implementations for sale. I do not believe that someone that spends months to reach a production grade state of his echo canceller just share it without compensation. Of course I can imagine that there are draft implementations made as student activity or quite working libs donated by IC manufacturer. (in case of libs you will not get sources, only .h interfaces.) Maybe the specialized "echo canceller" chip exists and you will be happy with it, I do not know. Maybe draft quality implementation available in sources is all you need, I do not know either.
I see you are new in this area. Here are some keywords for the beginning: acoustic or line, canceller or suppressor (in combinations).
For example the algorithm behind "Hands Free" mode in old PSTN phone sets is "Acoustic Echo Suppressor".
Good starting reference for suppressors is ITU-T G.164 https://www.itu.int/rec/T-REC-G.164-198811-I/en
At least you should know what exactly you are searching for.