Install libopenr2-dev by entering the following commands in the terminal:
sudo apt update sudo apt install libopenr2-dev
MFC/R2 (telephony) call setup library - development headers
OpenR2 is a library that implements the MFC/R2 telephony signalling over E1 lines using the DAHDI Telephony interface. . The MFC/R2 protocol is a telephony signalling protocol, widely used in Latin America, China and Africa, similar to the ISDN protocols found in most of Europe and North America . This package contains libraries and header files for developing applications.