The Logitech Harmony database lists the Luxman L-509x as being compatible with their universal remotes. To make that work you buy one of their remotes, connect it to your computer, go to their database at the URL below, type in the brand and model number of your Luxman remote and download the codes to the remote. I've been happily using that database for years with a variety of brands, though not with Luxman. Here's the Harmon site,
https://support.myharmony.com/en-us/compatibility