since I had no success using indi_usbfocus_focuser with EKOS, I finally decided to start my own (experimental) driver project for the USB_focus_V3. I already submitted some code to Jasem. I think if he finds that the code fits the quality requirements of libindi, he maybe can make a version available for testing.
I also started my own version using Moonlite focuser code as base and replacing the commands and some of the logic. Seems to work enough for EKOS autofocus to work and so on, haven't finished the temperature compensation changes yet. So it might be useful to combine the effort
My code is available at github.com/XXgeoXX/indi. Is seems that we pretty much went the same road. I also used the MoonLite focuser code as a basis for implementing the driver. The commands you send to the focuser controller look similar to mine. My code should basically be complete, including automatic temperature compensation, selecting rotation direction as well as changing the temperature compensation sign. However, since I only own one USB_focus_v3 and have no access to other samples, it up to now has only been tested with my device, having firmware 1505 installed on it.