The original implementation of LPD was in the Berkeley printing system in the BSD UNIX operating system; the LPRng project also supports that protocol.
The Common Unix Printing System (or CUPS), which is more common on modern Linux distributions and also found on macOS, supports LPD as well as the Internet Printing Protocol (IPP).
Commercial solutions are available that also use Berkeley printing protocol components, where more robust functionality and performance is necessary than is available from LPR/LPD (or CUPS) alone (such as might be required in large corporate environments).
[1] A server for the LPD protocol listens for requests on TCP port 515.
Note that the LPD queue name is case sensitive.