The upstream ABI of libjsoncpp has changed, and libjsoncpp1 is not available in later releases. The project you point to has a buggy bootstrap script, it should be pointing at libjsoncpp-dev only, not at a specific soname of the runtime library.
** Changed in: libjsoncpp (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to libjsoncpp in Ubuntu. https://bugs.launchpad.net/bugs/1928695 Title: unable to install libjsoncpp-1 on ubuntu 21.04 Status in libjsoncpp package in Ubuntu: Invalid Bug description: Machine details: Hardware: Raspberrypi4B OS: ubuntu 21.04 Issue: when trying to install openthread as per the installation procedure in the path: https://openthread.io/codelabs/openthread-border-router#1 it fails to install libjsoncpp1. When tried to install via apt-get, it says package cannot be located. # apt-get install libjsoncpp1 Reading package list... Done Building dependency tree... Done Reading state information... Done E: Unable to locate package libjsoncpp1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libjsoncpp/+bug/1928695/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp