packet-net apt repository

  curl -fsSL https://packet-net.github.io/apt/pubkey.asc | sudo gpg --dearmor -o /usr/share/keyrings/packet-net.gpg
  echo "deb [signed-by=/usr/share/keyrings/packet-net.gpg] https://packet-net.github.io/apt ./" | sudo tee /etc/apt/sources.list.d/packet-net.list
  sudo apt update
  sudo apt install dapps pdn-soundmodem axcall axinetd axlisten axsocks axtun packetnet pdn-bbs pdn-bpqchat pdn-convers pdn-libax25 pdn-net pdn-qso tait-codeplug tait-cli nprflash

See https://github.com/packet-net/apt for details.