I used a Raspberry Pi4 with mine, was basically plug and play. Installed a 'Barebones' image, one time calibration and could play stuff from NES - Dreamcast and a few arcade games. PC was easy to set up as well and worked perfectly with the HoTD Remake.
You might want to do some other tests or maybe contact Andy Sinden to see if there is actually something wrong with your LG?
Same for me. At some point I'll try the PC route again to make sure the gun is working OK. I'm thinking it might just be the lounge has too many reflections for it which will mean it's useless for me.
Out of interest what TV/Monitor are you both using as well? I had no issues in a fairly bright room with my B9 OLED, but my old Plasma Panasonic GT30 is probably a bit too reflective in certain conditions. I also preferred playing in darker conditions with my PC monitor.
I think light conditions / reflections can cause issues.