It stands for ‘Generic System Image’, I’ve used one before and it was mostly bare and service-less, but that has been a minute. One thing I’d note is that it was a pain in the ass and there were extra steps and requirements that if I had bothered to read I wouldn’t have messed with and just gone with AOSP.










Not sure of the intricacies of your hardware, this one does look like a pain in the ass, but there appears to be a LineageOS development build for at least one variant of a Moto G Stylus 5G on xda-developers.
https://xdaforums.com/t/rom-16-0-unofficial-lineageos-23-for-motorola-moto-g-stylus-5g-denver.4758372/