I created flashable phh's SuperUser for phhusson source based Treble GSIs. This archive changes only system image with minimal changing. This mean that you dont lose stability.
After flash you need install APK from Google Play https://play.google.com/store/apps/d....phh.superuser or from attachments.
Flash archive phh's-superuser.zip in TWRP or similar recovery for install.
phh's-superuser.zip is universal archive for ab and aonly systems. But if you got error try special ab or aonly archive.
Archive based on LineageOS addonsu.