Sergey,
I'm the maintainer of the Alpine Linux Kamailio package. The TLS module has never worked with Kamailio because of the use of LibreSSL.
Even after we got the patches to compile, the TLS module didn't actually work. So we pulled the patches and disabled the module entirely.
We are waiting for Alpine Linux to switch back to OpenSSL, and then will renable the module. Last I was informed, that will be the 3.8 or 3.9 release.
HTH