Honestly, make an issue in the OpenRGB Gitlab.

I got a Roccat Pyro that didn't work, and when I found that out, I was able to test someone's pull requests before they were merged.

Yes. Ratbag has support for many devices.

If all else fails, you can always spin up a Windows VM. I generally keep one around for tasks like this (or complex Excel workbooks).

I am using ckb-next for my Corsair mouse and keyboard. Just check if your mouse is supported.

One thing I couldn't so in Linux is save light settings to the on-board memory. For that I had to open Windows and the Corsair iCue software and save it from there. After that my mouse and keyboard boots with correct light colors

Your primary search term here should be the USB ID. Model numbers can help but so many things are rebadged or go through cost optimization where different revisions require entirely different drivers.

Plug in the device and see what dmesg or lsusb says. Search for that device ID, if you don't find any good matches search for the manufacturer ID -- frequently a newer model builds on older models code bases and APi.