I don’t use Home Assistant OS, but I know it’s very strict with regard to unsupported libraries(with good reason). So I would suggest using another vm or other solution to install xled_plus. In my case I created a python virtual environment in a Raspberry Pi, running raspbian (now Raspberry Pi OS), that also happened to be running HA Core. A Fedora VM should work but might be overkill for just running xled_plus. Regardless, start by getting xled_plus installed somewhere and to the point of running some of the examples manually from the command line before moving on to integrating it with Home Assistant.
The xled_plus project wasn’t created with Home Assistant in mind, so there’s no simple direct communication between the two. My solution was to use shell commands and python scripts to facilitate calling the xled_plus functions from outside of Home Assistant. For simply controlling on/off and brightness, I used the native Home Assistant Twinkly integration.
Once you have xled_plus working from the command line, getting Home Assistant to control XLED using my shell commands method, but from Home Assistant OS, will require doing some setup work using this guide for SSH’ing from a command line sensor or shell command. I can’t help here since I’m not on the HAOS and probably won’t be until (at least) the end of the holiday season.
My tree is still in the attic for another week or so (will probably be setting it up the weekend of Nov. 25th/26th. When I do have it up again, I can walk through my old setup and see if I can provide a clearer set of directions for setting up the HA and xled_plus scripts.