libosip2-dev 4.1.0-2.1 (armhf binary) in ubuntu focal

 libosip2 header files and static libraries to assist in development of
 programs wishing to use SIP.
 .
 The oSIP library is written in C, is thread safe and has no dependencies
 except the standard C library.
 .
 oSIP could be used to implement an IP soft-phone as well as embedded SIP
 software. oSIP is not limited to endpoint agents implementations and can
 also be used to implement SIP proxies or registration services.
 .
 oSIP currently provides an API for the SIP message parser, SDP message
 parser, and library to handle "SIP transactions" as defined by the SIP
 standards (RFC3261).